带有 mutate 和 ifelse 的新列，但在 R 中保留 NA

Question

I have a simple question but it is giving me a hard time.

I wish to recode a varibale with a ifelse function but I want to keep the NAs (in the variable "party") as NAs.

This is what I am doing. I have a variable with vote choice ("party") and I want to recode a new variable ("RRP") if participants choose a specific set of parties:

df<- df %>%
  mutate(RRP = if_else(party %in% c("4",#SPP/UDC
                                    "12",#Swiss Democrats
                                    "13",#FDU
                                    "14", #PSL
                                    "15"), 1, 0))

The problem is that participants who have NAs in the "party" variable are now being recoded as 0 because they don't fullfil the condition in ifelse.

I also tried this:

df<- df %>%
  mutate(RRP = if_else(party %in% c("4",#SPP/UDC
                                    "12",#Swiss Democrats
                                    "13",#FDU
                                    "14", #PSL
                                    "15"), 1, 0,  na.rm=TRUE))

but it just yield an error.

Do you have any other ideas?

Thanks a lot!

Answer 1

%in% returns FALSE for NA value and not NA . So when use it in ifelse / if_else it executes the FALSE condition in them. We can use case_when here:

library(dplyr)

df %>%
  mutate(RRP = case_when(party %in% c(4, 12:15) ~ 1, 
                         is.na(party) ~ NA_real_, 
                          TRUE ~ 0))
#  party RRP
#1    13   1
#2    14   1
#3    15   1
#4    16   0
#5    17   0
#6    NA  NA

data

df <- data.frame(party = c(13:17, NA))