Hi all,
Using R v2.7.1, platform i386-pc-mingw32
Can someone please shed some light on the behaviour of ifelse() for me?
My intent is to calc relative proportions of z$b, at the same time
subsetting z$b based on z$a. I could attack the problem other ways
(suggestions welcome) but I am also intrigued by the _order_ in which
ifelse seems to assign values, and how recycling works. For instance,
z <- data.frame(a = c(1,2,3,4,1), b = 6:10)
z$c <- ifelse(z$a > 1, z$b[z$a > 1]/sum(z$b[z$a > 1]), NA)
z # seems to have filled z$c by row 4,2,3
a b c
1 1 6 NA
2 2 7 0.3333333
3 3 8 0.3750000
4 4 9 0.2916667
5 1 10 NA
z$b[z$a > 1]/sum(z$b[z$a > 1]) # order looks fine here
[1] 0.2916667 0.3333333 0.3750000
z$d <- ifelse(z$a > 1, 6:8, NA) # fills by row 4,2,3 (as above) z$e <-
ifelse(z$a > 1, 6:7, NA) # recycling, but why values 7,6,7 instead of
6,7,6 ?
z
a b c d e
1 1 6 NA NA NA
2 2 7 0.3333333 7 7
3 3 8 0.3750000 8 6
4 4 9 0.2916667 6 7
5 1 10 NA NA NA
TIA for any insight into how ifelse is filling/recycling in this
instance. I know there's not much code in ifelse, but it's still not
immediately apparent to me why I'm getting what I'm seeing.
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Applied Statistics
Southern Ocean Ecosystems
Australian Antarctic Division, Tasmania
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