On 19/07/2009 5:17 PM, Mark Knecht wrote:
Hi,
In my data.frame I wanted to essentially write
If(Test) c*d else c+d
but that doesn't work. I found I could do it mathematically, but it
seems forced and won't scale well for nested logic. I have two
examples below writing columns e & f, but I don't think the code is
self-documenting as it depends on knowing that Test is a TRUE/FALSE.
Is there a better way to do the following?
Thanks,
Mark
DF <- data.frame(cbind(a=1:4, b=1:2, c=1:8, d=1:16, e=0, f=0))
DF$Test <- with(DF, a == b)
DF$e = (DF$c*DF$d) * DF$Test + (DF$c+DF$d) * !DF$Test
DF$f = with(DF, (c*d)*Test + (c+d)*!Test)
Use ifelse().
DF$f <- with(DF, ifelse(a == b, c*d, c+d))
Duncan Murdoch
DF
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