从R中的数据框中删除行时NA值出现问题

Question

This is my data frame:

ID <- c('TZ1','TZ2','TZ3','TZ4')
hr <- c(56,32,38,NA)
cr <- c(1,4,5,2)
data <- data.frame(ID,hr,cr)

   ID hr cr
1 TZ1 56  1
2 TZ2 32  4
3 TZ3 38  5
4 TZ4 NA  2

I want to remove the rows where data$hr = 56. This is what I want the end product to be:

   ID hr cr
2 TZ2 32  4
3 TZ3 38  5
4 TZ4 NA  2

This is what I thought would work:

data = data[data$hr !=56,]

However the resulting data frame looks like this:

     ID hr cr
2   TZ2 32  4
3   TZ3 38  5
NA <NA> NA NA

How can I mofify my code to encorporate the NA value so this doesn't happen? Thank you for your help, I can't figure it out.

EDIT: I also want to keep the NA value in the data frame.

Answer 1

The issue is that when we do the == or != , if there are NA values, it will remain as such and create an NA row for that corresponding NA value. So one way to make the logical index with only TRUE/FALSE values will be to use is.na also in the comparison.

 data[!(data$hr==56 & !is.na(data$hr)),]
 #   ID hr cr
 #2 TZ2 32  4
 #3 TZ3 38  5
 #4 TZ4 NA  2

We could also apply the reverse logic

subset(data, hr!=56|is.na(hr))
#   ID hr cr
#2 TZ2 32  4
#3 TZ3 38  5
#4 TZ4 NA  2