Hello,
I wrote a version of which.na (similar to S's) in R that returns a
vector of positions at which NA appears in the target vector v:
which.na<-function(v) {
retv <- c()
for (i in 1:length(v)) {
if (is.na(v[i])) {
retv<-append(i, retv, after = length(retv))
}
}
return(retv)
}
nv <- c(2,4,NA,NA)
nas<-which.r(nv)
print(nas)
[run]
> source("which.r")
[1] 4 3
>
Two questions about this:
(1) It seems that append actually "prepends"
(2) Is there a more simpler way to build the vector of positions (versus
using append in a loop, as above), using functions such as match() and
apply()?
Thank You.
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