[R] Skip last NA's?

[J. Hosking]

Robert Lundqvist wrote:
> I wonder if anyone could help me find an expression for skipping the last
> missing values in a vector? The kind of material I have is something like
> 
> x<-c(23,12,NA,23,24,21,NA,NA,NA)
> 
> I would like to skip the last NA's, but not the ones in between other
> vallues. Any hints? (Why not do this by simply take x[1:6]? I have several
> vectors a couple of thousand observations long with varying numbers of
> NA's in the end. I'd prefer not to search through all of these one at a
> time.)
> 
> Robert
> 
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x[1:max(which(!is.na(x)))]

or, to allow for cases in which x may consist entirely of NAs or have 
length 0,

x[0:max(0,which(!is.na(x)))]