How to subset data in R without losing NA rows?

Question

I have some data that I am looking at in R. One particular column, titled \"Height\", contains a few rows of NA.

I am looking to subset my data-frame so that all He

Answer 1

For subsetting by character/factor variables, you can use %in% to keep NAs. Specify the data you wish to exclude.

# Create Dataset
library(data.table)
df=data.table(V1=c('Surface','Bottom',NA),V2=1:3)
df
#         V1 V2
# 1: Surface  1
# 2:  Bottom  2
# 3:      3

# Keep all but 'Bottom'
df[!V1 %in% c('Bottom')]
#         V1 V2
# 1: Surface  1
# 2:      3

This works because %in% never returns an NA (see ?match)