[R] ifelse choices in a data.frame?

[Duncan Murdoch]

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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