metamorphr: Tidy and Streamlined Metabolomics Data Workflows

Description

Facilitate tasks typically encountered during metabolomics data analysis including data import, filtering, missing value imputation (Stacklies et al. (2007) doi:10.1093/bioinformatics/btm069, Stekhoven et al. (2012) doi:10.1093/bioinformatics/btr597, Tibshirani et al. (2017) doi:10.18129/B9.BIOC.IMPUTE, Troyanskaya et al. (2001) doi:10.1093/bioinformatics/17.6.520), normalization (Bolstad et al. (2003) doi:10.1093/bioinformatics/19.2.185, Dieterle et al. (2006) doi:10.1021/ac051632c, Zhao et al. (2020) doi:10.1038/s41598-020-72664-6) transformation, centering and scaling (Van Den Berg et al. (2006) doi:10.1186/1471-2164年7月14日2) as well as statistical tests and plotting. 'metamorphr' introduces a tidy (Wickham et al. (2019) doi:10.21105/joss.01686) format for metabolomics data and is designed to make it easier to build elaborate analysis workflows and to integrate them with 'tidyverse' packages including 'dplyr' and 'ggplot2'.

Author(s)

Maintainer: Yannik Schermer yannik.schermer@chem.rptu.de (ORCID) [copyright holder]

See Also

Useful links:

• https://github.com/yasche/metamorphr

• Report bugs at https://github.com/yasche/metamorphr/issues

Pipe operator

Description

See magrittr::%>% for details.

Usage

lhs %>% rhs

Arguments

Value

The result of calling rhs(lhs).

A tibble containing the NIST standard atomic weights

Description

The data set contains the atomic weights of the elements and their isotopes. It is used to calculate the exact mass in formula_to_mass but can also be used as a reference.

description

Usage

atoms

Format

atoms

A data frame with 442 rows and 7 columns:

Number

The atomic number of the element in the periodic table.

Element

The element.

Isotope

The mass number of the specific isotope.

Symbol

The atomic symbol. Either only the letter (for standard isotopes) or the mass number followed by the symbol (for special isotopes).

Weight

The monoisotopic mass of the isotope.

Composition

The fraction of the isotope in the naturally occuring element.

Standard_Weight

The standard atomic weight of the element. It is the sum of the product of the Weight and Composition column for each element. Where no composition is available, the weight of the IUPAC "ATOMIC WEIGHTS OF THE ELEMENTS 2023" table was used. See the Source section for more information.

...

Source

The table was retrieved from the National Institute of Standards and Technology (NIST) at https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl, accesed in October 2025, and enriched with data from the IUPAC "ATOMIC WEIGHTS OF THE ELEMENTS 2023" table at https://iupac.qmul.ac.uk/AtWt/, accesed in October 2025

Calculate the Kendrick mass

Description

Calculate the Kendrick mass for a given mass (or m/z) and repeating unit. The Kendrick mass is a rescaled mass, that usually sets CH2 = 14 but other repeating units can also be used. It is usefull for the visual identification of potential homologues. See the References section for more information. The Kendrick mass is not to be confused with the Kendrick mass defect (KMD, calc_kmd ) and the nominal Kendrick mass (calc_nominal_km ).

Usage

calc_km(mass, repeating_unit = "CH2")

Arguments

Value

The Kendrick mass.

References

• Kendrick mass on Wikipedia

• Edward Kendrick, Anal. Chem. 1963, 35, 2146–2154.

• C. A. Hughey, C. L. Hendrickson, R. P. Rodgers, A. G. Marshall, K. Qian, Anal. Chem. 2001, 73, 4676–4681.

Examples

# Calculate the Kendrick masses for two measured masses with
# CH2 as the repeating unit.
# See Hughey et al. in the References section above
calc_km(c(351.3269, 365.3425))
# Construct a KMD plot from m/z values.
# RT is mapped to color and the feature-wise maximum intensity to size.
# Note that in the publication by Hughey et al., the nominal Kendrick mass
# is used on the x-axis instead of the exact Kendrick mass.
# See ?calc_nominal_km.
toy_metaboscape %>%
 dplyr::group_by(UID, `m/z`, RT) %>%
 dplyr::summarise(max_int = max(Intensity, na.rm = TRUE)) %>%
 dplyr::ungroup() %>%
 dplyr::mutate(KMD = calc_kmd(`m/z`),
 KM = calc_km(`m/z`)) %>%
 ggplot2::ggplot(ggplot2::aes(x = KM,
 y = KMD,
 size = max_int,
 color = RT)) +
 ggplot2::geom_point()

Calculate the Kendrick mass defect (KMD)

Description

The Kendrick mass defect (KMD) is calculated by subtracting the Kendrick mass (calc_km ) from the nominal Kendrick mass (calc_nominal_km ). The the References section for more information.

Usage

calc_kmd(mass, repeating_unit = "CH2")

Arguments

Value

The Kendrick mass defect (KMD)

References

• Kendrick mass on Wikipedia

• Edward Kendrick, Anal. Chem. 1963, 35, 2146–2154.

• C. A. Hughey, C. L. Hendrickson, R. P. Rodgers, A. G. Marshall, K. Qian, Anal. Chem. 2001, 73, 4676–4681.

Examples

# Calculate the Kendrick mass defects for two measured masses with
# CH2 as the repeating unit.
# See Hughey et al. in the References section above
calc_kmd(c(351.3269, 365.3425))
# Construct a KMD plot from m/z values.
# RT is mapped to color and the feature-wise maximum intensity to size.
toy_metaboscape %>%
 dplyr::group_by(UID, `m/z`, RT) %>%
 dplyr::summarise(max_int = max(Intensity, na.rm = TRUE)) %>%
 dplyr::ungroup() %>%
 dplyr::mutate(KMD = calc_kmd(`m/z`),
 `nominal KM` = calc_nominal_km(`m/z`)) %>%
 ggplot2::ggplot(ggplot2::aes(x = `nominal KM`,
 y = KMD,
 size = max_int,
 color = RT)) +
 ggplot2::geom_point()

Calculate neutral losses from precursor ion mass and fragment ion masses

Description

Calculate neutral loss spectra for all ions with available MSn spectra in data. To calculate neutral losses, MSn spectra are required. See read_mgf . This step is required for subsequent filtering based on neutral losses (filter_neutral_loss ). Resulting neutral loss spectra are stored in tibbles in a new list column named Neutral_Loss.

Usage

calc_neutral_loss(data, m_z_col)

Arguments

Value

A tibble with added neutral loss spectra. A new list column is created named Neutral_Loss.

Examples

toy_mgf %>%
 calc_neutral_loss(m_z_col = PEPMASS)

Calculate the nominal Kendrick mass

Description

The nominal Kendrick mass is the Kendrick mass (calc_km ), rounded up to the nearest whole number. The nominal Kendrick mass and the Kendrick mass are both required to calculate the Kendrick mass defect (KMD). The nominal Kendrick mass is not to be confused with the Kendrick mass defect (calc_kmd ) and the Kendrick mass (calc_km ).

Usage

calc_nominal_km(mass, repeating_unit = "CH2")

Arguments

Value

The nominal Kendrick mass.

References

• Kendrick mass on Wikipedia

• Edward Kendrick, Anal. Chem. 1963, 35, 2146–2154.

• C. A. Hughey, C. L. Hendrickson, R. P. Rodgers, A. G. Marshall, K. Qian, Anal. Chem. 2001, 73, 4676–4681.

Examples

# Calculate the nominal Kendrick masses for two measured masses with
# CH2 as the repeating unit.
# See Hughey et al. in the References section above
calc_nominal_km(c(351.3269, 365.3425))
# Construct a KMD plot from m/z values.
# RT is mapped to color and the feature-wise maximum intensity to size.
toy_metaboscape %>%
 dplyr::group_by(UID, `m/z`, RT) %>%
 dplyr::summarise(max_int = max(Intensity, na.rm = TRUE)) %>%
 dplyr::ungroup() %>%
 dplyr::mutate(KMD = calc_kmd(`m/z`),
 `nominal KM` = calc_nominal_km(`m/z`)) %>%
 ggplot2::ggplot(ggplot2::aes(x = `nominal KM`,
 y = KMD,
 size = max_int,
 color = RT)) +
 ggplot2::geom_point()

Collapse intensities of technical replicates by calculating their maximum

Description

Calculates the minimum of the intensity of technical replicates (e.g., if the same sample was injected multiple times or if multiple workups have been performed on the same starting material). The function assigns new sample names by joining either group and replicate name, or if a batch column is specified group, replicate and batch together with a specified separator. Due to the nature of the function, sample and feature metadata columns will be dropped unless they are specified with the according arguments.

Usage

collapse_max(
 data,
 group_column = .data$Group,
 replicate_column = .data$Replicate,
 batch_column = .data$Batch,
 feature_metadata_cols = "Feature",
 sample_metadata_cols = NULL,
 separator = "_"
)

Arguments

Value

A tibble with intensities of technical replicates collapsed.

Examples

# uses a slightly modified version of toy_metaboscape_metadata
collapse_toy_metaboscape_metadata <- toy_metaboscape_metadata
collapse_toy_metaboscape_metadata$Replicate <- 1
toy_metaboscape %>%
 join_metadata(collapse_toy_metaboscape_metadata) %>%
 impute_lod() %>%
 collapse_max(group_column = Group, replicate_column = Replicate)

Collapse intensities of technical replicates by calculating their mean

Description

Calculates the mean of the intensity of technical replicates (e.g., if the same sample was injected multiple times or if multiple workups have been performed on the same starting material). The function assigns new sample names by joining either group and replicate name, or if a batch column is specified group, replicate and batch together with a specified separator. Due to the nature of the function, sample and feature metadata columns will be dropped unless they are specified with the according arguments.

Usage

collapse_mean(
 data,
 group_column = .data$Group,
 replicate_column = .data$Replicate,
 batch_column = .data$Batch,
 feature_metadata_cols = "Feature",
 sample_metadata_cols = NULL,
 separator = "_"
)

Arguments

Value

A tibble with intensities of technical replicates collapsed.

Examples

# uses a slightly modified version of toy_metaboscape_metadata
collapse_toy_metaboscape_metadata <- toy_metaboscape_metadata
collapse_toy_metaboscape_metadata$Replicate <- 1
toy_metaboscape %>%
 join_metadata(collapse_toy_metaboscape_metadata) %>%
 impute_lod() %>%
 collapse_mean(group_column = Group, replicate_column = Replicate)

Collapse intensities of technical replicates by calculating their median

Description

Calculates the median of the intensity of technical replicates (e.g., if the same sample was injected multiple times or if multiple workups have been performed on the same starting material). The function assigns new sample names by joining either group and replicate name, or if a batch column is specified group, replicate and batch together with a specified separator. Due to the nature of the function, sample and feature metadata columns will be dropped unless they are specified with the according arguments.

Usage

collapse_median(
 data,
 group_column = .data$Group,
 replicate_column = .data$Replicate,
 batch_column = .data$Batch,
 feature_metadata_cols = "Feature",
 sample_metadata_cols = NULL,
 separator = "_"
)

Arguments

Value

A tibble with intensities of technical replicates collapsed.

Examples

# uses a slightly modified version of toy_metaboscape_metadata
collapse_toy_metaboscape_metadata <- toy_metaboscape_metadata
collapse_toy_metaboscape_metadata$Replicate <- 1
toy_metaboscape %>%
 join_metadata(collapse_toy_metaboscape_metadata) %>%
 impute_lod() %>%
 collapse_median(group_column = Group, replicate_column = Replicate)

Collapse intensities of technical replicates by calculating their minimum

Description

Calculates the minimum of the intensity of technical replicates (e.g., if the same sample was injected multiple times or if multiple workups have been performed on the same starting material). The function assigns new sample names by joining either group and replicate name, or if a batch column is specified group, replicate and batch together with a specified separator. Due to the nature of the function, sample and feature metadata columns will be dropped unless they are specified with the according arguments.

Usage

collapse_min(
 data,
 group_column = .data$Group,
 replicate_column = .data$Replicate,
 batch_column = .data$Batch,
 feature_metadata_cols = "Feature",
 sample_metadata_cols = NULL,
 separator = "_"
)

Arguments

Value

A tibble with intensities of technical replicates collapsed.

Examples

# uses a slightly modified version of toy_metaboscape_metadata
collapse_toy_metaboscape_metadata <- toy_metaboscape_metadata
collapse_toy_metaboscape_metadata$Replicate <- 1
toy_metaboscape %>%
 join_metadata(collapse_toy_metaboscape_metadata) %>%
 impute_lod() %>%
 collapse_min(group_column = Group, replicate_column = Replicate)

Create a blank metadata skeleton

Description

Takes a tidy tibble created by metamorphr::read_featuretable() and returns an empty tibble for sample metadata. The tibble can either be populated directly in R or exported and edited by hand (e.g. in Excel). Metadata are necessary for several downstream functions. More columns may be added if necessary.

Usage

create_metadata_skeleton(data)

Arguments

Value

An empty tibble structure with the necessary columns for metadata:

Sample

The sample name

Group

To which group does the samples belong? For example a treatment or a background. Note that additional columns with additional grouping information can be freely added if necessary.

Replicate

If multiple technical replicates exist in the data set, they must have the same value for Replicate and the same value for Group so that they can be collapsed. Examples for technical replicates are: the same sample was injected multiple times or workup was performed multiple times with the same starting material. If no technical replicates exist, set Replicate = 1 for all samples.

Batch

The batch in which the samples were prepared or measured. If only one batch exists, set Batch = 1 for all samples.

Factor

A sample-specific factor, for example dry weight or protein content.

...

Examples

featuretable_path <- system.file("extdata", "toy_metaboscape.csv", package = "metamorphr")
metadata <- read_featuretable(featuretable_path, metadata_cols = 2:5) %>%
 create_metadata_skeleton()

Filter Features based on their occurrence in blank samples

Description

Filters Features based on their occurrence in blank samples. For example, if min_frac = 3 the maximum intensity in samples must be at least 3 times as high as in blanks for a Feature not to be filtered out.

Usage

filter_blank(
 data,
 blank_samples,
 min_frac = 3,
 blank_as_group = FALSE,
 group_column = NULL
)

Arguments

Value

A filtered tibble.

Examples

# Example 1: Define blanks by sample name
toy_metaboscape %>%
 filter_blank(blank_samples = c("Blank1", "Blank2"), blank_as_group = FALSE, min_frac = 3)
# Example 2: Define blanks by group name
# toy_metaboscape %>%
# join_metadata(toy_metaboscape_metadata) %>%
# filter_blank(blank_samples = "blank",
# blank_as_group = TRUE,
# min_frac = 3,
# group_column = Group)

Filter Features based on their coefficient of variation

Description

Filters Features based on their coefficient of variation (CV). The CV is defined as CV = \frac{s_i}{\overline{x_i}} with s_i = Standard deviation of sample i and \overline{x_i} = Mean of sample i.

Usage

filter_cv(
 data,
 reference_samples,
 max_cv = 0.2,
 ref_as_group = FALSE,
 group_column = NULL,
 na_as_zero = TRUE
)

Arguments

Value

A filtered tibble.

References

Coefficient of Variation on Wikipedia

Examples

# Example 1: Define reference samples by sample names
toy_metaboscape %>%
 filter_cv(max_cv = 0.2, reference_samples = c("QC1", "QC2", "QC3"))
# Example 2: Define reference samples by group name
toy_metaboscape %>%
 join_metadata(toy_metaboscape_metadata) %>%
 filter_cv(max_cv = 0.2, reference_samples = "QC", ref_as_group = TRUE, group_column = Group)

Filter Features based on the absolute number or fraction of samples it was found in

Description

Filters features based on the number or fraction of samples they are found in. This is usually one of the first steps in metabolomics data analysis and often already performed when the feature table is first created from the raw spectral files..

Usage

filter_global_mv(data, min_found = 0.5, fraction = TRUE)

Arguments

Value

A filtered tibble.

Examples

# Example 1: A feature must be found in at least 50 % of the samples
toy_metaboscape %>%
 filter_global_mv(min_found = 0.5)
# Example 2: A feature must be found in at least 8 samples
toy_metaboscape %>%
 filter_global_mv(min_found = 8, fraction = FALSE)

Group-based feature filtering

Description

Similar to filter_global_mv it filters features that are found in a specified number of samples. The key difference is that filter_grouped_mv() takes groups into consideration and therefore needs sample metadata. For example, if fraction = TRUE and min_found = 0.5, a feature must be found in at least 50 % of the samples of at least 1 group. It is very similar to the Filter features by occurrences in groups option in Bruker MetaboScape.

Usage

filter_grouped_mv(
 data,
 min_found = 0.5,
 group_column = .data$Group,
 fraction = TRUE
)

Arguments

Value

A filtered tibble.

Examples

# A Feature must be found in all samples of at least 1 group.
toy_metaboscape %>%
 join_metadata(toy_metaboscape_metadata) %>%
 filter_grouped_mv(min_found = 1, group_column = Group)

Filter Features based on occurrence of fragment ions

Description

Filters Features based on the presence of MSn fragments. This can help, for example with the identification of potential homologous molecules.

Usage

filter_msn(
 data,
 fragments,
 min_found,
 tolerance = 5,
 tolerance_type = "ppm",
 show_progress = TRUE
)

Arguments

Value

A filtered tibble.

Examples

# all of the given fragments (3) must be found
# returns the first row of toy_mgf
toy_mgf %>%
 filter_msn(fragments = c(12.3456, 23.4567, 34.5678), min_found = 3)
# all of the given fragments (3) must be found
# returns an empty tibble because the third fragment
# of row 1 (34.5678)
# is outside of the tolerance (5 ppm):
# Lower bound:
# 34.5688 - 34.5688 * 5 / 1000000 = 34.5686
# Upper bound:
# 34.5688 + 34.5688 * 5 / 1000000 = 34.5690
toy_mgf %>%
 filter_msn(fragments = c(12.3456, 23.4567, 34.5688), min_found = 3)
# only 2 of the 3 fragments must be found
# returns the first row of toy_mgf
toy_mgf %>%
 filter_msn(fragments = c(12.3456, 23.4567, 34.5688), min_found = 2)

Filter Features based on their mass-to-charge ratios

Description

Facilitates filtering by given mass-to-charge ratios (m/z) with a defined tolerance. Can also be used to filter based on exact mass.

Usage

filter_mz(data, m_z_col, masses, tolerance = 5, tolerance_type = "ppm")

Arguments

Value

A filtered tibble.

Examples

# Use a tolerance of plus or minus 5 ppm
toy_metaboscape %>%
 filter_mz(m_z_col = `m/z`, 162.1132, tolerance = 5, tolerance_type = "ppm")
# Use a tolerance of plus or minus 0.005 Da
toy_metaboscape %>%
 filter_mz(m_z_col = `m/z`, 162.1132, tolerance = 0.005, tolerance_type = "absolute")

Filter Features based on occurrence of neutral losses

Description

The occurrence of characteristic neutral losses can help with the putative annotation of molecules. See the Reference section for an example.

Usage

filter_neutral_loss(
 data,
 losses,
 min_found,
 tolerance = 10,
 tolerance_type = "ppm",
 show_progress = TRUE
)

Arguments

Value

A filtered tibble.

References

• A. Brink, F. Fontaine, M. Marschmann, B. Steinhuber, E. N. Cece, I. Zamora, A. Pähler, Rapid Commun. Mass Spectrom. 2014, 28, 2695–2703, DOI 10.1002/rcm.7062.

Examples

# neutral losses must be calculated first
toy_mgf_nl <- toy_mgf %>%
 calc_neutral_loss(m_z_col = PEPMASS)
# all of the given losses (3) must be found
# returns the first row of toy_mgf
toy_mgf_nl %>%
 filter_neutral_loss(losses = c(11.1111, 22.2222, 33.3333), min_found = 3)
# all of the given fragments (3) must be found
# returns an empty tibble because the third loss
# of row 1 (33.3333)
# is outside of the tolerance (10 ppm):
# Lower bound:
# 33.4333 - 33.4333 * 5 / 1000000 = 33.4333
# Upper bound:
# 33.4333 + 33.4333 * 5 / 1000000 = 33.4336
toy_mgf_nl %>%
 filter_neutral_loss(losses = c(11.1111, 22.2222, 33.4333), min_found = 3)
# only 2 of the 3 fragments must be found
# returns the first row of toy_mgf
toy_mgf_nl %>%
 filter_neutral_loss(losses = c(11.1111, 22.2222, 33.4333), min_found = 2)

Calculate the monoisotopic mass from a given formula

Description

Calculates the monoisotopic mass from a given formula. If only the element symbols are provided, the calculated mass corresponds to that of a molecule made up from the most abundant isotopes. Other isotopes can also be provided (e.g., ¹³C, instead of the naturally most abundant ¹²C). See the samples for details.

Usage

formula_to_mass(formula)

Arguments

Value

The monoisotopic mass of the formula.

Examples

# The monoisotopic mass is calculated with the most abundant isotopes
# if only the element symbols are provided:
formula_to_mass("CH4")
formula_to_mass("NH3")
formula_to_mass("C10H17N3O6S")
# Other isotopes can be provided as follows:
formula_to_mass("[13C]H4")
formula_to_mass("[15N]H3")
# Every isotope, including the most abundant ones, can be named explicitly.
# Compare:
formula_to_mass("[14N][1H]3")
formula_to_mass("NH3")
# The function also supports brackets and nested brackets:
formula_to_mass("(CH3)2")
formula_to_mass("(((CH3)2N)3C)2")
formula_to_mass("((([13C]H3)2N)3C)2")

Impute missing values using Bayesian PCA

Description

One of several PCA-based imputation methods. Basically a wrapper around ⁠pcaMethods::⁠pca (method = "bpca"). For a detailed discussion, see the vignette("pcaMethods") and vignette("missingValues", "pcaMethods") as well as the References section.

Important Note

impute_bpca() depends on the pcaMethods package from Bioconductor. If metamorphr was installed via install.packages(), dependencies from Bioconductor were not automatically installed. When impute_bpca() is called without the pcaMethods package installed, you should be asked if you want to install pak and pcaMethods. If you want to use impute_bpca() you have to install those. In case you run into trouble with the automatic installation, please install pcaMethods manually. See pcaMethods – a Bioconductor package providing PCA methods for incomplete data.

Usage

impute_bpca(data, n_pcs = 2, center = TRUE, scale = "none", direction = 2)

Arguments

Value

A tibble with imputed missing values.

References

• H. R. Wolfram Stacklies, 2017, DOI 10.18129/B9.BIOC.PCAMETHODS.

• W. Stacklies, H. Redestig, M. Scholz, D. Walther, J. Selbig, Bioinformatics 2007, 23, 1164–1167, DOI 10.1093/bioinformatics/btm069.

Examples

toy_metaboscape %>%
 impute_bpca()

Impute missing values by replacing them with the lowest observed intensity (global)

Description

Replace missing intensity values (NA) with the lowest observed intensity.

Usage

impute_global_lowest(data)

Arguments

Value

A tibble with imputed missing values.

Examples

toy_metaboscape %>%
 impute_global_lowest()

Impute missing values using nearest neighbor averaging

Description

Basically a wrapper function around ⁠impute::⁠impute.knn . Imputes missing values using the k-th nearest neighbor algorithm.

Note that the function ln-transforms the data prior to imputation and transforms it back to the original scale afterwards. Please do not do it manually prior to calling impute_knn()! See References for more information.

Important Note

impute_knn() depends on the impute package from Bioconductor. If metamorphr was installed via install.packages(), dependencies from Bioconductor were not automatically installed. When impute_knn() is called without the impute package installed, you should be asked if you want to install pak and impute. If you want to use impute_knn() you have to install those. In case you run into trouble with the automatic installation, please install impute manually. See impute: Imputation for microarray data for instructions on manual installation.

Usage

impute_knn(data, quietly = TRUE, ...)

Arguments

Value

A tibble with imputed missing values.

References

• Robert Tibshirani, Trevor Hastie, 2017, DOI 10.18129/B9.BIOC.IMPUTE.

• J. Khan, J. S. Wei, M. Ringnér, L. H. Saal, M. Ladanyi, F. Westermann, F. Berthold, M. Schwab, C. R. Antonescu, C. Peterson, P. S. Meltzer, Nat Med 2001, 7, 673–679, DOI 10.1038/89044.

Examples

toy_metaboscape %>%
 impute_knn()

Impute missing values using Local Least Squares (LLS)

Description

Basically a wrapper around ⁠pcaMethods::⁠llsImpute . For a detailed discussion, see the vignette("pcaMethods") and vignette("missingValues", "pcaMethods") as well as the References section.

Important Note impute_lls() depends on the pcaMethods package from Bioconductor. If metamorphr was installed via install.packages(), dependencies from Bioconductor were not automatically installed. When impute_svd() is called without the pcaMethods package installed, you should be asked if you want to install pak and pcaMethods. If you want to use impute_lls() you have to install those. In case you run into trouble with the automatic installation, please install pcaMethods manually. See pcaMethods – a Bioconductor package providing PCA methods for incomplete data for instructions on manual installation.

Usage

impute_lls(
 data,
 correlation = "pearson",
 complete_genes = FALSE,
 center = FALSE,
 cluster_size = 10
)

Arguments

Value

A tibble with imputed missing values.

References

• H. R. Wolfram Stacklies, 2017, DOI 10.18129/B9.BIOC.PCAMETHODS.

• W. Stacklies, H. Redestig, M. Scholz, D. Walther, J. Selbig, Bioinformatics 2007, 23, 1164–1167, DOI 10.1093/bioinformatics/btm069.

Examples

# The cluster size must be reduced because
# the data set is too small for the default (10)
toy_metaboscape %>%
 impute_lls(complete_genes = TRUE, cluster_size = 5)

Impute missing values by replacing them with the Feature 'Limit of Detection'

Description

Replace missing intensity values (NA) by what is assumed to be the detector limit of detection (LoD). It is estimated by dividing the Feature minimum by the provided denominator, usually 5. See the References section for more information.

Usage

impute_lod(data, div_by = 5)

Arguments

Value

A tibble with imputed missing values.

References

LoD on OmicsForum

Examples

toy_metaboscape %>%
 impute_lod()

Impute missing values by replacing them with the Feature mean

Description

Replace missing intensity values (NA) with the Feature mean of non-NA values. For example, if a Feature has the measured intensities ⁠NA, 1, NA, 3, 2⁠ in samples 1-5, the intensities after impute_mean() would be ⁠2, 1, 2, 3, 2⁠.

Usage

impute_mean(data)

Arguments

Value

A tibble with imputed missing values.

Examples

toy_metaboscape %>%
 impute_mean()

Impute missing values by replacing them with the Feature median

Description

Replace missing intensity values (NA) with the Feature median of non-NA values. For example, if a Feature has the measured intensities ⁠NA, 1, NA, 3, 2⁠ in samples 1-5, the intensities after impute_median() would be ⁠2, 1, 2, 3, 2⁠.

Usage

impute_median(data)

Arguments

Value

A tibble with imputed missing values.

Examples

toy_metaboscape %>%
 impute_median()

Impute missing values by replacing them with the Feature minimum

Description

Replace missing intensity values (NA) with the Feature minimum of non-NA values.

Usage

impute_min(data)

Arguments

Value

A tibble with imputed missing values.

Examples

toy_metaboscape %>%
 impute_min()

Impute missing values using NIPALS PCA

Description

One of several PCA-based imputation methods. Basically a wrapper around ⁠pcaMethods::⁠pca (method = "nipals"). For a detailed discussion, see the vignette("pcaMethods") and vignette("missingValues", "pcaMethods") as well as the References section.

Important Note

impute_nipals() depends on the pcaMethods package from Bioconductor. If metamorphr was installed via install.packages(), dependencies from Bioconductor were not automatically installed. When impute_nipals() is called without the pcaMethods package installed, you should be asked if you want to install pak and pcaMethods. If you want to use impute_nipals() you have to install those. In case you run into trouble with the automatic installation, please install pcaMethods manually. See pcaMethods – a Bioconductor package providing PCA methods for incomplete data for instructions on manual installation.

Usage

impute_nipals(data, n_pcs = 2, center = TRUE, scale = "none", direction = 2)

Arguments

Value

A tibble with imputed missing values.

References

• H. R. Wolfram Stacklies, 2017, DOI 10.18129/B9.BIOC.PCAMETHODS.

• W. Stacklies, H. Redestig, M. Scholz, D. Walther, J. Selbig, Bioinformatics 2007, 23, 1164–1167, DOI 10.1093/bioinformatics/btm069.

Examples

toy_metaboscape %>%
 impute_nipals()

Impute missing values using Probabilistic PCA

Description

One of several PCA-based imputation methods. Basically a wrapper around ⁠pcaMethods::⁠pca (method = "ppca"). For a detailed discussion, see the vignette("pcaMethods") and vignette("missingValues", "pcaMethods") as well as the References section.
In the underlying function (⁠pcaMethods::⁠pca (method = "ppca")), the order of columns has an influence on the outcome. Therefore, calling ⁠pcaMethods::⁠pca (method = "ppca") on a matrix and calling metamorphr::impute() on a tidy tibble might give different results, even though they contain the same data. That is because under the hood, the tibble is transformed to a matrix prior to calling ⁠pcaMethods::⁠pca (method = "ppca") and you have limited influence on the column order of the resulting matrix.

Important Note

impute_ppca() depends on the pcaMethods package from Bioconductor. If metamorphr was installed via install.packages(), dependencies from Bioconductor were not automatically installed. When impute_ppca() is called without the pcaMethods package installed, you should be asked if you want to install pak and pcaMethods. If you want to use impute_ppca() you have to install those. In case you run into trouble with the automatic installation, please install pcaMethods manually. See pcaMethods – a Bioconductor package providing PCA methods for incomplete data for instructions on manual installation.

Usage

impute_ppca(
 data,
 n_pcs = 2,
 center = TRUE,
 scale = "none",
 direction = 2,
 random_seed = 1L
)

Arguments

Value

A tibble with imputed missing values.

References

• H. R. Wolfram Stacklies, 2017, DOI 10.18129/B9.BIOC.PCAMETHODS.

• W. Stacklies, H. Redestig, M. Scholz, D. Walther, J. Selbig, Bioinformatics 2007, 23, 1164–1167, DOI 10.1093/bioinformatics/btm069.

Examples

toy_metaboscape %>%
 impute_ppca()

Impute missing values using random forest

Description

Basically a wrapper function around ⁠missForest::⁠missForest . Imputes missing values using the random forest algorithm.

Usage

impute_rf(data, random_seed = 1L, ...)

Arguments

Value

A tibble with imputed missing values.

References

• missForest on CRAN

• D. J. Stekhoven, P. Bühlmann, Bioinformatics 2012, 28, 112–118, DOI 10.1093/bioinformatics/btr597.

Examples

toy_metaboscape %>%
 impute_rf()

Impute missing values using Singular Value Decomposition (SVD)

Description

Basically a wrapper around ⁠pcaMethods::⁠pca (method = "svdImpute"). For a detailed discussion, see the vignette("pcaMethods") and vignette("missingValues", "pcaMethods") as well as the References section.

Important Note impute_svd() depends on the pcaMethods package from Bioconductor. If metamorphr was installed via install.packages(), dependencies from Bioconductor were not automatically installed. When impute_svd() is called without the pcaMethods package installed, you should be asked if you want to install pak and pcaMethods. If you want to use impute_svd() you have to install those. In case you run into trouble with the automatic installation, please install pcaMethods manually. See pcaMethods – a Bioconductor package providing PCA methods for incomplete data for instructions on manual installation.

Usage

impute_svd(data, n_pcs = 2, center = TRUE, scale = "none", direction = 2)

Arguments

Value

A tibble with imputed missing values.

References

• H. R. Wolfram Stacklies, 2017, DOI 10.18129/B9.BIOC.PCAMETHODS.

• W. Stacklies, H. Redestig, M. Scholz, D. Walther, J. Selbig, Bioinformatics 2007, 23, 1164–1167, DOI 10.1093/bioinformatics/btm069.

• O. Troyanskaya, M. Cantor, G. Sherlock, P. Brown, T. Hastie, R. Tibshirani, D. Botstein, R. B. Altman, Bioinformatics 2001, 17, 520–525, DOI 10.1093/bioinformatics/17.6.520.

Examples

toy_metaboscape %>%
 impute_svd()

Impute missing values by replacing them with a user-provided value

Description

Replace missing intensity values (NA) with a user-provided value (e.g., 1).

Usage

impute_user_value(data, value)

Arguments

Value

A tibble with imputed missing values.

Examples

toy_metaboscape %>%
 impute_user_value(value = 1)

Join a featuretable and sample metadata

Description

Joins a featuretable and associated sample metadata. Basically a wrapper around left_join where by = "Sample".

Usage

join_metadata(data, metadata)

Arguments

Value

A tibble with added sample metadata.

Examples

toy_metaboscape %>%
 join_metadata(toy_metaboscape_metadata)

Normalize intensities across samples using cyclic LOESS normalization

Description

The steps the algorithm takes are the following:

1. log2 transform the intensities

2. Choose 2 samples to generate an MA-plot from

3. Fit a LOESS curve

4. Subtract half of the difference between the predicted value and the true value from the intensity of sample 1 and add the same amount to the intensity of Sample 2

5. Repeat for all unique combinations of samples

6. Repeat all steps until the model converges or n_iter is reached.

Convergence is assumed if the confidence intervals of all LOESS smooths include the 0 line. If fixed_iter = TRUE, the algorithm will perform exactly n_iter iterations. If fixed_iter = FALSE, the algorithm will perform a maximum of n_iter iterations.

See the reference section for details.

Usage

normalize_cyclic_loess(
 data,
 n_iter = 3,
 fixed_iter = TRUE,
 loess_span = 0.7,
 level = 0.95,
 verbose = FALSE,
 ...
)

Arguments

Value

A tibble with intensities normalized across samples.

References

• B. M. Bolstad, R. A. Irizarry, M. Åstrand, T. P. Speed, Bioinformatics 2003, 19, 185–193, DOI 10.1093/bioinformatics/19.2.185.

• Karla Ballman, Diane Grill, Ann Oberg, Terry Therneau, "Faster cyclic loess: normalizing DNA arrays via linear models" can be found under https://www.mayo.edu/research/documents/biostat-68pdf/doc-10027897, 2004.

• K. V. Ballman, D. E. Grill, A. L. Oberg, T. M. Therneau, Bioinformatics 2004, 20, 2778–2786, DOI 10.1093/bioinformatics/bth327.

Examples

toy_metaboscape %>%
 impute_lod() %>%
 normalize_cyclic_loess()

Normalize intensities across samples using a normalization factor

Description

Normalization is done by dividing the intensity by a sample-specific factor (e.g., weight, protein or DNA content). This function requires a sample-specific factor, usually supplied via the Factor column from the sample metadata. See the Examples section for details.

Usage

normalize_factor(data, factor_column = .data$Factor)

Arguments

Value

A tibble with intensities normalized across samples.

Examples

toy_metaboscape %>%
 join_metadata(toy_metaboscape_metadata) %>%
 normalize_factor()

Normalize intensities across samples by dividing by the sample median

Description

Normalize across samples by dividing feature intensities by the sample median, making the median 1 in all samples. See References for more information.

Usage

normalize_median(data)

Arguments

Value

A tibble with intensities normalized across samples.

References

T. Ramirez, A. Strigun, A. Verlohner, H.-A. Huener, E. Peter, M. Herold, N. Bordag, W. Mellert, T. Walk, M. Spitzer, X. Jiang, S. Sperber, T. Hofmann, T. Hartung, H. Kamp, B. Van Ravenzwaay, Arch Toxicol 2018, 92, 893–906, DOI 10.1007/s00204-017-2079-6.

Examples

toy_metaboscape %>%
 normalize_median()

Normalize intensities across samples using a Probabilistic Quotient Normalization (PQN)

Description

This method was originally developed for H-NMR spectra of complex biofluids but has been adapted for other 'omics data. It aims to eliminate dilution effects by calculating the most probable dilution factor for each sample, relative to one or more reference samples. See references for more details.

Usage

normalize_pqn(
 data,
 fn = "median",
 normalize_sum = TRUE,
 reference_samples = NULL,
 ref_as_group = FALSE,
 group_column = NULL
)

Arguments

Value

A tibble with intensities normalized across samples.

References

• F. Dieterle, A. Ross, G. Schlotterbeck, H. Senn, Anal. Chem. 2006, 78, 4281–4290, DOI 10.1021/ac051632c.

Examples

# specify the reference samples with their sample names
toy_metaboscape %>%
 impute_lod() %>%
 normalize_pqn(reference_samples = c("QC1", "QC2", "QC3"))
# specify the reference samples with their group names
toy_metaboscape %>%
 join_metadata(toy_metaboscape_metadata) %>%
 impute_lod() %>%
 normalize_pqn(reference_samples = c("QC"), ref_as_group = TRUE, group_column = Group)

Normalize intensities across samples using standard Quantile Normalization

Description

This is the standard approach for Quantile Normalization. Other sub-flavors are also available:

• normalize_quantile_group

• normalize_quantile_batch

• normalize_quantile_smooth

See References for more information.

Usage

normalize_quantile_all(data)

Arguments

Value

A tibble with intensities normalized across samples.

References

Y. Zhao, L. Wong, W. W. B. Goh, Sci Rep 2020, 10, 15534, DOI 10.1038/s41598-020-72664-6.

Examples

toy_metaboscape %>%
 normalize_quantile_all()

Normalize intensities across samples using grouped Quantile Normalization with multiple batches

Description

This function performs a Quantile Normalization on each sub-group and batch in the data set. It therefore requires grouping information. See Examples for more information. This approach might perform better than the standard approach, normalize_quantile_all , if sub-groups are very different (e.g., when comparing cancer vs. normal tissue).

Other sub-flavors are also available:

• normalize_quantile_all

• normalize_quantile_batch

• normalize_quantile_smooth

See References for more information. Note that it is equivalent to the 'Discrete' normalization in Zhao et al. but has been renamed for internal consistency.

Usage

normalize_quantile_batch(
 data,
 group_column = .data$Group,
 batch_column = .data$Batch
)

Arguments

Value

A tibble with intensities normalized across samples.

References

Y. Zhao, L. Wong, W. W. B. Goh, Sci Rep 2020, 10, 15534, DOI 10.1038/s41598-020-72664-6.

Examples

toy_metaboscape %>%
 # Metadata, including grouping and batch information,
 # must be added before using normalize_quantile_batch()
 join_metadata(toy_metaboscape_metadata) %>%
 normalize_quantile_batch(group_column = Group, batch_column = Batch)

Normalize intensities across samples using grouped Quantile Normalization

Description

This function performs a Quantile Normalization on each sub-group in the data set. It therefore requires grouping information. See Examples for more information. This approach might perform better than the standard approach, normalize_quantile_all , if sub-groups are very different (e.g., when comparing cancer vs. normal tissue).

Other sub-flavors are also available:

• normalize_quantile_all

• normalize_quantile_batch

• normalize_quantile_smooth

See References for more information. Note that it is equivalent to the 'Class-specific' normalization in Zhao et al. but has been renamed for internal consistency.

Usage

normalize_quantile_group(data, group_column = .data$Group)

Arguments

Value

A tibble with intensities normalized across samples.

References

Y. Zhao, L. Wong, W. W. B. Goh, Sci Rep 2020, 10, 15534, DOI 10.1038/s41598-020-72664-6.

Examples

toy_metaboscape %>%
 # Metadata, including grouping information, must be added before using normalize_quantile_group()
 join_metadata(toy_metaboscape_metadata) %>%
 normalize_quantile_group(group_column = Group)

Normalize intensities across samples using smooth Quantile Normalization (qsmooth)

Description

This function performs a smooth Quantile Normalization on each sub-group in the data set (qsmooth). It therefore requires grouping information. See Examples for more information. This approach might perform better than the standard approach, normalize_quantile_all , if sub-groups are very different (e.g., when comparing cancer vs. normal tissue). The result lies somewhere between normalize_quantile_group and normalize_quantile_all . Basically a re-implementation of Hicks et al. (2018).

Usage

normalize_quantile_smooth(
 data,
 group_column = .data$Group,
 rolling_window = 0.05
)

Arguments

Value

A tibble with intensities normalized across samples.

References

• S. C. Hicks, K. Okrah, J. N. Paulson, J. Quackenbush, R. A. Irizarry, H. C. Bravo, Biostatistics 2018, 19, 185–198, DOI 10.1093/biostatistics/kxx028.

• Y. Zhao, L. Wong, W. W. B. Goh, Sci Rep 2020, 10, 15534, DOI 10.1038/s41598-020-72664-6.

Examples

toy_metaboscape %>%
 # Metadata, including grouping information, must be added before using normalize_quantile_group()
 join_metadata(toy_metaboscape_metadata) %>%
 normalize_quantile_smooth(group_column = Group)

Normalize intensities across samples using a reference feature

Description

Performs a normalization based on a reference feature, for example an internal standard. Divides the Intensities of all features by the Intensity of the reference feature in that sample and multiplies them with a constant value, making the Intensity of the reference feature the same in each sample.

Usage

normalize_ref(
 data,
 reference_feature,
 identifier_column,
 reference_feature_intensity = 1
)

Arguments

Value

A tibble with intensities normalized across samples.

Examples

# Divide by the reference feature and make its Intensity 1000 in each sample
toy_metaboscape %>%
 impute_lod() %>%
 normalize_ref(reference_feature = 2, identifier_column = UID, reference_feature_intensity = 1000)
# Divide by the reference feature and make its Intensity the mean of intensities
# of the reference features before normalization
toy_metaboscape %>%
 impute_lod() %>%
 normalize_ref(reference_feature = 2, identifier_column = UID, reference_feature_intensity = mean)

Normalize intensities across samples by dividing by the sample sum

Description

Normalize across samples by dividing feature intensities by the sum of all intensities in a sample, making the sum 1 in all samples.

Important Note

Intensities of individual features will be very small after this normalization approach. It is therefore advised to multiply all intensities with a fixed number (e.g., 1000) after normalization. See this discussion on OMICSForum.ca and the examples below for further information.

Usage

normalize_sum(data)

Arguments

Value

A tibble with intensities normalized across samples.

Examples

# Example 1: Normalization only
toy_metaboscape %>%
 normalize_sum()
# Example 2: Multiply with 1000 after normalization
toy_metaboscape %>%
 normalize_sum() %>%
 dplyr::mutate(Intensity = .data$Intensity * 1000)

Draws a scores or loadings plot or performs calculations necessary to draw them manually

Description

Performs PCA and creates a Scores or Loadings plot. Basically a wrapper around ⁠pcaMethods::⁠pca The plot is drawn with ggplot2 and can therefore be easily manipulated afterwards (e.g., changing the theme or the axis labels). Please note that the function is intended to be easy to use and beginner friendly and therefore offers limited ability to fine-tune certain parameters of the resulting plot. If you wish to draw the plot yourself, you can set return_tbl = TRUE. In this case, a tibble is returned instead of a ggplot2 object which you can use to create a plot yourself.

Important Note

plot_pca() depends on the pcaMethods package from Bioconductor. If metamorphr was installed via install.packages(), dependencies from Bioconductor were not automatically installed. When plot_pca() is called without the pcaMethods package installed, you should be asked if you want to install pak and pcaMethods. If you want to use plot_pca() you have to install those. In case you run into trouble with the automatic installation, please install pcaMethods manually. See pcaMethods – a Bioconductor package providing PCA methods for incomplete data for instructions on manual installation.

Usage

plot_pca(
 data,
 method = "svd",
 what = "scores",
 n_pcs = 2,
 pcs = c(1, 2),
 center = TRUE,
 group_column = NULL,
 name_column = NULL,
 return_tbl = FALSE,
 verbose = FALSE
)

Arguments

Value

Either a Scores or Loadings Plot in the form of a ggplot2 object or a tibble.

Examples

# Draw a Scores Plot
toy_metaboscape %>%
 impute_lod() %>%
 join_metadata(toy_metaboscape_metadata) %>%
 plot_pca(what = "scores", group_column = Group)
# Draw a Loadings Plot
toy_metaboscape %>%
 impute_lod() %>%
 join_metadata(toy_metaboscape_metadata) %>%
 plot_pca(what = "loadings", name_column = Feature)

Draws a Volcano Plot or performs calculations necessary to draw one manually

Description

Performs necessary calculations (i.e., calculate p-values and log2-fold changes) and creates a basic Volcano Plot. The plot is drawn with ggplot2 and can therefore be easily manipulated afterwards (e.g., changing the theme or the axis labels). Please note that the function is intended to be easy to use and beginner friendly and therefore offers limited ability to fine-tune certain parameters of the resulting plot. If you wish to draw the plot yourself, you can set return_tbl = TRUE. In this case, a tibble is returned instead of a ggplot2 object which you can use to create a plot yourself. A Volcano Plot is used to compare two groups. Therefore grouping information must be provided. See join_metadata for more information.

Usage

plot_volcano(
 data,
 group_column,
 name_column,
 groups_to_compare,
 batch_column = NULL,
 batch = NULL,
 log2fc_cutoff = 1,
 p_value_cutoff = 0.05,
 colors = list(sig_up = "darkred", sig_down = "darkblue", not_sig_up = "grey",
 not_sig_down = "grey", not_sig = "grey"),
 adjust_p = FALSE,
 log2_before = FALSE,
 return_tbl = FALSE,
 ...
)

Arguments

Value

Either a Volcano Plot in the form of a ggplot2 object or a tibble.

Examples

# returns a Volcano Plot in the form of a ggplot2 object
toy_metaboscape %>%
 impute_lod() %>%
 join_metadata(toy_metaboscape_metadata) %>%
 plot_volcano(
 group_column = Group,
 name_column = Feature,
 groups_to_compare = c("control", "treatment")
 )
# returns a tibble to draw the plot manually
toy_metaboscape %>%
 impute_lod() %>%
 join_metadata(toy_metaboscape_metadata) %>%
 plot_volcano(
 group_column = Group,
 name_column = Feature,
 groups_to_compare = c("control", "treatment"),
 return_tbl = TRUE
 )

Read a feature table into a tidy tibble

Description

Basically a wrapper around readr::read_delim() but performs some initial tidying operations such as gather() rearranging columns. The label_col will be renamed to Feature.

Usage

read_featuretable(file, delim = ",", label_col = 1, metadata_cols = NULL, ...)

Arguments

Value

A tidy tibble.

References

• H. Wickham, J. Stat. Soft. 2014, 59, DOI 10.18637/jss.v059.i10.

• H. Wickham, M. Averick, J. Bryan, W. Chang, L. McGowan, R. François, G. Grolemund, A. Hayes, L. Henry, J. Hester, M. Kuhn, T. Pedersen, E. Miller, S. Bache, K. Müller, J. Ooms, D. Robinson, D. Seidel, V. Spinu, K. Takahashi, D. Vaughan, C. Wilke, K. Woo, H. Yutani, JOSS 2019, 4, 1686, DOI 10.21105/joss.01686.

• "12 Tidy data | R for Data Science," can be found under https://r4ds.had.co.nz/tidy-data.html, 2023.

Examples

# Read a toy dataset in the format produced with Bruker MetaboScape (Version 2021).
featuretable_path <- system.file("extdata", "toy_metaboscape.csv", package = "metamorphr")
# Example 1: Provide indices for metadata_cols
featuretable <- read_featuretable(featuretable_path, metadata_cols = 2:5)
featuretable
# Example 2: Provide a name for label_col and indices for metadata_cols
featuretable <- read_featuretable(
 featuretable_path,
 label_col = "m/z",
 metadata_cols = c(1, 2, 4, 5)
)
featuretable
# Example 3: Provide names for both, label_col and metadata_cols
featuretable <- read_featuretable(
 featuretable_path,
 label_col = "m/z",
 metadata_cols = c("Bucket label", "RT", "Name", "Formula")
)
featuretable

Read a MGF file into a tidy tibble

Description

MGF files allow the storage of MS/MS spectra. With this function they can be read into a tidy tibble. Each variable is stored in a column and each ion (observation) is stored in a separate row. MS/MS spectra are stored in a list column named MSn.
Please note that MGF files are software-specific so the variables and their names may vary. This function was developed with the GNPS file format exported from mzmine in mind.

Usage

read_mgf(file, show_progress = TRUE)

Arguments

Value

A tidy tibble holding MS/MS spectra.

Examples

mgf_path <- system.file("extdata", "toy_mgf.mgf", package = "metamorphr")
read_mgf(mgf_path)

Scale intensities of features using autoscale

Description

Scales the intensities of all features using

\widetilde{x}_{ij}=\frac{x_{ij}-\overline{x}_{i}}{s_i}

where \widetilde{x}_{ij} is the intensity of sample j, feature i after scaling, x_{ij} is the intensity of sample j, feature i before scaling, \overline{x}_{i} is the mean of intensities of feature i across all samples and {s_i} is the standard deviation of intensities of feature i across all samples. In other words, it subtracts the mean intensity of a feature across samples from the intensities of that feature in each sample and divides by the standard deviation of that feature. For more information, see the reference section.

Usage

scale_auto(data)

Arguments

Value

A tibble with autoscaled intensities.

References

• R. A. Van Den Berg, H. C. Hoefsloot, J. A. Westerhuis, A. K. Smilde, M. J. Van Der Werf, BMC Genomics 2006, 7, 142, DOI 10.1186/1471-2164年7月14日2.

Examples

toy_metaboscape %>%
 scale_auto()

Center intensities of features around zero

Description

Centers the intensities of all features around zero using

\widetilde{x}_{ij}=x_{ij}-\overline{x}_{i}

where \widetilde{x}_{ij} is the intensity of sample j, feature i after scaling, x_{ij} is the intensity of sample j, feature i before scaling and \overline{x}_{i} is the mean of intensities of feature i across all samples. In other words, it subtracts the mean intensity of a feature across samples from the intensities of that feature in each sample. For more information, see the reference section.

Usage

scale_center(data)

Arguments

Value

A tibble with intensities scaled around zero.

References

• R. A. Van Den Berg, H. C. Hoefsloot, J. A. Westerhuis, A. K. Smilde, M. J. Van Der Werf, BMC Genomics 2006, 7, 142, DOI 10.1186/1471-2164年7月14日2.

Examples

toy_metaboscape %>%
 scale_center()

Scale intensities of features using level scaling

Description

Scales the intensities of all features using

\widetilde{x}_{ij}=\frac{x_{ij}-\overline{x}_{i}}{\overline{x}_{i}}

where \widetilde{x}_{ij} is the intensity of sample j, feature i after scaling, x_{ij} is the intensity of sample j, feature i before scaling and \overline{x}_{i} is the mean of intensities of feature i across all samples

In other words, it performs centering (scale_center ) and divides by the feature mean, thereby focusing on the relative intensity.

Usage

scale_level(data)

Arguments

Value

A tibble with level scaled intensities.

References

• R. A. Van Den Berg, H. C. Hoefsloot, J. A. Westerhuis, A. K. Smilde, M. J. Van Der Werf, BMC Genomics 2006, 7, 142, DOI 10.1186/1471-2164年7月14日2.

Examples

toy_metaboscape %>%
 impute_lod() %>%
 scale_level()

Scale intensities of features using Pareto scaling

Description

Scales the intensities of all features using

\widetilde{x}_{ij}=\frac{x_{ij}-\overline{x}_{i}}{\sqrt{s_i}}

where \widetilde{x}_{ij} is the intensity of sample j, feature i after scaling, x_{ij} is the intensity of sample j, feature i before scaling, \overline{x}_{i} is the mean of intensities of feature i across all samples and {\sqrt{s_i}} is the square root of the standard deviation of intensities of feature i across all samples. In other words, it subtracts the mean intensity of a feature across samples from the intensities of that feature in each sample and divides by the square root of the standard deviation of that feature. For more information, see the reference section.

Usage

scale_pareto(data)

Arguments

Value

A tibble with autoscaled intensities.

References

• R. A. Van Den Berg, H. C. Hoefsloot, J. A. Westerhuis, A. K. Smilde, M. J. Van Der Werf, BMC Genomics 2006, 7, 142, DOI 10.1186/1471-2164年7月14日2.

Examples

toy_metaboscape %>%
 scale_pareto()

Scale intensities of features using range scaling

Description

Scales the intensities of all features using

\widetilde{x}_{ij}=\frac{x_{ij}-\overline{x}_{i}}{x_{i,max}-x_{i,min}}

where \widetilde{x}_{ij} is the intensity of sample j, feature i after scaling, x_{ij} is the intensity of sample j, feature i before scaling, \overline{x}_{i} is the mean of intensities of feature i across all samples, x_{i,max} is the maximum intensity of feature i across all samples and x_{i,min} is the minimum intensity of feature i across all samples. In other words, it subtracts the mean intensity of a feature across samples from the intensities of that feature in each sample and divides by the range of that feature. For more information, see the reference section.

Usage

scale_range(data)

Arguments

Value

A tibble with range scaled intensities.

References

• R. A. Van Den Berg, H. C. Hoefsloot, J. A. Westerhuis, A. K. Smilde, M. J. Van Der Werf, BMC Genomics 2006, 7, 142, DOI 10.1186/1471-2164年7月14日2.

Examples

toy_metaboscape %>%
 scale_range()

Scale intensities of features using vast scaling

Description

Scales the intensities of all features using

\widetilde{x}_{ij}=\frac{x_{ij}-\overline{x}_{i}}{s_i}\cdot \frac{\overline{x}_{i}}{s_i}

where \widetilde{x}_{ij} is the intensity of sample j, feature i after scaling, x_{ij} is the intensity of sample j, feature i before scaling, \overline{x}_{i} is the mean of intensities of feature i across all samples and {s_i} is the standard deviation of intensities of feature i across all samples. Note that \frac{\overline{x}_{i}}{s_i} = \frac{{1}}{CV} where CV is the coefficient of variation across all samples. scale_vast_grouped is a variation of this function that uses a group-specific coefficient of variation. In other words, it performs autoscaling (scale_auto ) and divides by the coefficient of variation, thereby reducing the importance of features with a poor reproducibility.

Usage

scale_vast(data)

Arguments

Value

A tibble with vast scaled intensities.

References

• R. A. Van Den Berg, H. C. Hoefsloot, J. A. Westerhuis, A. K. Smilde, M. J. Van Der Werf, BMC Genomics 2006, 7, 142, DOI 10.1186/1471-2164年7月14日2.

• J. Sun, Y. Xia, Genes & Diseases 2024, 11, 100979, DOI 10.1016/j.gendis.2023年04月01日8.

Examples

toy_metaboscape %>%
 scale_vast()

Scale intensities of features using grouped vast scaling

Description

A variation of scale_vast but uses a group-specific coefficient of variation and therefore requires group information. See scale_vast and the References section for more information.

Usage

scale_vast_grouped(data, group_column = .data$Group)

Arguments

Value

A tibble with vast scaled intensities.

References

• R. A. Van Den Berg, H. C. Hoefsloot, J. A. Westerhuis, A. K. Smilde, M. J. Van Der Werf, BMC Genomics 2006, 7, 142, DOI 10.1186/1471-2164年7月14日2.

Examples

toy_metaboscape %>%
 join_metadata(toy_metaboscape_metadata) %>%
 scale_vast_grouped()

General information about a feature table and sample-wise summary

Description

Information about a feature table. Prints information to the console (number of samples, number of features and if applicable number of groups, replicates and batches) and returns a sample-wise summary as a list.

Usage

summary_featuretable(
 data,
 n_samples_max = 5,
 n_features_max = 5,
 n_groups_max = 5,
 n_batches_max = 5
)

Arguments

Value

A sample-wise summary as a list.

Examples

toy_metaboscape %>%
 join_metadata(toy_metaboscape_metadata) %>%
 summary_featuretable()

A small toy data set created from a feature table in MetaboScape style

Description

The raw feature table is also included. This tibble can be reproduced with metamorphr::read_featuretable(system.file("extdata", "toy_metaboscape.csv", package = "metamorphr"), metadata_cols = 2:5).

Usage

toy_metaboscape

Format

toy_metaboscape

A data frame with 110 rows and 8 columns:

UID

A unique identifier for each Feature. This column is automatically generated by metamorphr::read_featuretable() when the feature table is imported.

Feature

A label given to each Feature for easier identification. The column of the original feature table that is used to generate the Feature column is specified with the label_col argument of metamorphr::read_featuretable().

Sample

Sample name. Column names in the original feature table.

Intensity

Measured intensity (or area).

RT

Retention time. Feature metadata and therefore not really necessary.

m/z

Mass over charge. Feature metadata and therefore not really necessary.

Name

Feature name. Feature metadata and therefore not really necessary.

Formula

Chemical formula. Feature metadata and therefore not really necessary.

...

Source

This data set contains fictional data!

Sample metadata for the fictional dataset toy_metaboscape

Description

Data was generated with metamorphr::create_metadata_skeleton() and can be reproduced with metamorphr::toy_metaboscape %>% create_metadata_skeleton().'

Usage

toy_metaboscape_metadata

Format

toy_metaboscape_metadata

A data frame with 11 rows and 5 columns:

Sample

The sample name

Group

To which group does the samples belong? For example a treatment or a background. Note that additional columns with additional grouping information can be freely added if necessary.

Replicate

The replicate.

Batch

The batch in which the samples were prepared or measured.

Factor

A sample-specific factor, for example dry weight or protein content.

...

Source

This data set contains fictional data!

A small toy data set containing MSn spectra

Description

Data was generated with metamorphr::read_mgf() and can be reproduced with This tibble can be reproduced with metamorphr::read_mgf(system.file("extdata", "toy_mgf.mgf", package = "metamorphr")).

Usage

toy_mgf

Format

toy_mgf

A data frame with 3 rows and 5 columns:

VARIABLEONE

A fictional variable.

VARIABLETWO

A fictional variable.

VARIABLETHREE

A fictional variable.

PEPMASS

The precursor ion m/z.

MSn

A list column containing MSn spectra.

...

Source

This data set contains fictional data!

Transforms the intensities by calculating their log

Description

Log-transforms intensities. The default (base = 10) calculates the log10. This transformation can help reduce heteroscedasticity. See references for more information.

Usage

transform_log(data, base = 10)

Arguments

Value

A tibble with log-transformed intensities.

References

• R. A. Van Den Berg, H. C. Hoefsloot, J. A. Westerhuis, A. K. Smilde, M. J. Van Der Werf, BMC Genomics 2006, 7, 142, DOI 10.1186/1471-2164年7月14日2.

Examples

toy_metaboscape %>%
 impute_lod() %>%
 transform_log()

Transforms the intensities by calculating their nth root

Description

Calculates the nth root of intensities with x^(1/n). The default (n = 2) calculates the square root. This transformation can help reduce heteroscedasticity. See references for more information.

Usage

transform_power(data, n = 2)

Arguments

Value

A tibble with power-transformed intensities.

References

• R. A. Van Den Berg, H. C. Hoefsloot, J. A. Westerhuis, A. K. Smilde, M. J. Van Der Werf, BMC Genomics 2006, 7, 142, DOI 10.1186/1471-2164年7月14日2.

Examples

toy_metaboscape %>%
 impute_lod() %>%
 transform_power()