Creating a new column from existing columns in a shapefile with a condition in R

Question

I have a shapefile that has multiple columns, and I am trying to merge columns X5andX1 into a new column class, such that only the NA rows of X5 get filled by the corresponding rows of X1. For example, in the new column the rows 1-4 will have values from rows 1-4 of X5, but rows 5-7will have value GRND from column X1. Similarly, then rows 8-9 of column class will be filled with values PLSE from X5 and so. Hope it makes sense. How can I do this in R. I am thinking of using dplyr and ifelse, but I am stuck.

Sample data

FID X1 X5 class
1 VEG PRPU 
2 VEG PRPU 
3 VEG PRPU 
4 VEG PRPU 
5 WTR NA 
6 WTR NA 
7 WTR NA 
8 VEG PLSE 
9 VEG PLSE 
10 GRND NA 
11 GRND NA 

Code

library(sf)
library(tidyverse)
# Load shapefile
shp = st_read("path", "filename")
# Create a new column class
shp %>% add_column(class = NA)
# Try 
shp %>% mutate(class = ifelse(class %in% "", X5, class)) # Stuck...

Answer 1

You were really close. You should use == instead of %in%.

shp %>% 
 mutate(class = ifelse(is.na(X5), X1, X5))
# FID X1 X5 class
#1 1 VEG PRPU PRPU
#2 2 VEG PRPU PRPU
#3 3 VEG PRPU PRPU
#4 4 VEG PRPU PRPU
#5 5 WTR WTR
#6 6 WTR WTR
#7 7 WTR WTR
#8 8 VEG PLSE PLSE
#9 9 VEG PLSE PLSE
#10 10 GRND GRND
#11 11 GRND GRND

• Arthur_Morgan: I am getting NA values where there were supposed to be X1 values in the class column.
• Jonathan V. Solórzano: Try checking if there are X5 entries filled with a blank space or something like that. That is probably causing those results.
• Arthur_Morgan: Yes you are right thank you, the empty rows shown in ArcGIS were actually being shown as NA in R. So doing, shp %>% dplyr::mutate(class = ifelse(is.na(X5), X1, X5)) fixes the issue. You can edit that in your answer to reflect that.

Answer 2

If the only issue is to resolve NAs, and you are using {dplyr} anyhow, you may consider dplyr::coalesce() for a somewhat more concise code.

library(dplyr)
shp <- tibble::tribble(~FID, ~X1, ~X5, 
 1, 'VEG', 'PRPU',
 2, 'VEG', 'PRPU',
 3, 'VEG', 'PRPU',
 4, 'VEG', 'PRPU',
 5, 'WTR', NA, 
 6, 'WTR', NA, 
 7, 'WTR', NA, 
 8, 'VEG', 'PLSE', 
 9, 'VEG', 'PLSE', 
 10, 'GRND', NA, 
 11, 'GRND', NA)
shp %>% 
 mutate(class = coalesce(X5, X1))
 FID X1 X5 class
 <dbl> <chr> <chr> <chr>
 1 1 VEG PRPU PRPU 
 2 2 VEG PRPU PRPU 
 3 3 VEG PRPU PRPU 
 4 4 VEG PRPU PRPU 
 5 5 WTR NA WTR 
 6 6 WTR NA WTR 
 7 7 WTR NA WTR 
 8 8 VEG PLSE PLSE 
 9 9 VEG PLSE PLSE 
10 10 GRND NA GRND 
11 11 GRND NA GRND