> -----Original Message-----
>
> You can check for an empty vector as follows:
> ...
> vals <- apply(plabor[c("colA","colB","colC")],1,function(x)
> length(na.omit(x)))
> vals # [1] 3 0 3 2
> <- ifelse(vals>0, plabor$colD, NA)
>
plabor
A slightly more compact variant that avoids the intermediate 'vals' variable is
to apply an anonymous function that does the check internally:
plabor$colD <- apply(plabor, 1, function(x) if(all(is.na(x))) NA else prod(x,
na.rm=TRUE))
S Ellison
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