如何在分配值时处理 NA

Question

I have a data frame x which includes two variables fdhm1 and fdhm2 . Now, I want to generate a new variable fdhm conditional on both values of fdhm1 and fdhm2 .

Specifically, if fdhm1 != NA and fdhm2 ==0 , fdhm <- fdhm1 . Otherwise, fdhm <- NA .

Here is my codes:

fdhm   <- NA
x   <- cbind(x,fdhm)
use   <- x$fdhm1 != NA & x$fdhm2 == 0
x$fdhm[use]   <- x$fdhm1[use]

but an error message popped up, saying that NAs are not allowed in subscripted assignments

I am not sure what the reason is?

Answer 1

You can try !is.na(x$fdhm1) (rather than x$fdhm1 != NA ), eg,

x <- within(x,fdhm <- ifelse(!is.na(fdhm1)&fdhm2==0,fdhm1,NA))

---

Here is an example showing you what happened.

Given a vector u like below

> u
[1] NA  2 NA  1 NA

then

> u!=NA
[1] NA NA NA NA NA

> !is.na(u)
[1] FALSE  TRUE FALSE  TRUE FALSE