Data 8

Table Functions and Methods

Name Chapter Description

Table 5 Create an empty table, usually to extend with data

Table.read_table 5 Create a table from a data file

with_columns 5 Create a copy of a table with more columns

column 5 Create an array containing the elements of a column

num_rows 5 Compute the number of rows in a table

num_columns 5 Compute the number of columns in a table

labels 5 Lists the column labels in a table

select 5 Create a copy of a table with only some of the columns

drop 5 Create a copy of a table without some of the columns

relabel 5 Modifies the existing table in place, changing the column heading in the first argument to the second

relabeled 5 Returns a new table with the column heading in the first argument changed to the second

sort 5.2 Create a copy of a table sorted by the values in a column. Defaults to ascending order unless "descending = True" is included

where 5.3 Create a copy of a table with only the rows that match some predicate

take 5.3 Create a copy of the table with only the rows whose indices are in the given array

barh 6.1 Draws a bar chart of the frequencies of a categorical distribution

histogram 6.2 Draws a histogram of a numerical distribution

apply 7.1 Returns an array of a a function applied to some row in a table

group 7.2 Create a copy of the table with all rows with the same values in a certain column aggregated into one row in the new table

groups 7.3 Create a copy of the table with all rows with the same value in a certain array of columns aggregated into one row in the new table

pivot 7.3 Create a copy of the table with a column for each element in the first argument and a row for each element in the second argument and aggregates values

join 7.4 Create a copy of the table that is the result of joining the columns of two tables, with a row for each shared value in the two tables

sample 9 Draws some number of rows at random from a table. By default, with replacement.

proportion_from_distribution 10.1 Returns a new table with an additional column corresponding to proportions from a random sample of some size of the proportions in a column.

Array Functions and Methods

Name Chapter Description

max 3.3 Returns the maximum value of an array

min 3.3 Returns the minimum value of an array

sum 3.3 Returns the sum of the values in an array

len 3.3 Returns the length (number of elements) of an array

make_array 4.4 Makes a numpy array with the values passed in

np.average 4.4 Returns the mean value of an array

np.std 12.2 Returns the standard deviation of an array of numbers

np.diff 4.4 Returns a new array of size len(arr)-1 with elements equal to the difference between adjacent elements

np.sqrt 4.4 Returns an array with the square root of each element

np.arange 4.5 Returns an array of an end-exclusive range of variable step size

arr.item 4.6 Returns the i-th item in an array (remember Python indices start at 0!)

np.random.choice 8 Picks one (by default) or some number 'n' of items from an array at random. By default, with replacement.

np.count_nonzero 8 Returns the number of non-zero (or True) elements in an array.

np.append 8.2 Returns a copy of the input array with some item (must be the same type as the other entries in the array) appended to the end.

percentile 11.1 Returns the corresponding percentile of an array.