I have a variable A containing continuous numeric values and a binary variable B. I would like to create a new variable A1 which contains the same values as A if B=1 and missing values (NA) if B=2. Many thanks!
3 Answers
You can use ifelse() for that:
a1 <- ifelse(B == 1, A, NA)
answered Feb 12, 2014 at 14:57
Christopher Louden
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Comments
Here's a simple and efficient approach without ifelse:
A <- 1:10
# [1] 1 2 3 4 5 6 7 8 9 10
B <- rep(1:2, 5)
# [1] 1 2 1 2 1 2 1 2 1 2
A1 <- A * NA ^ (B - 1)
# [1] 1 NA 3 NA 5 NA 7 NA 9 NA
Comments
You can use ifelse for this:
A = runif(100)
B = sample(c(0,1), 100, replace = TRUE)
B1 = ifelse(B == 1, A, NA)
You can even leave out the == 1 as R interprets 0 as FALSE and any other number as TRUE:
B1 = ifelse(B, A, NA)
Although the == 1 is both more flexible and makes it more clear what happens. So I'd go for the first approach.
ifelse, I guess you could also just indexAthroughB, i.e.A[B == 2] <- NA.