R help - Jul 2009 - ifelse choices in a data.frame?

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)

DF

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
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

use ifelse:
> 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$f = with(DF, (c*d)*Test + (c+d)*!Test)
> #or
> DF$f.1 <- ifelse(DF$Test, DF$c * DF$d, DF$c + DF$d)
> head(DF)
  a b c d  e  f  Test f.1
1 1 1 1 1  1  1  TRUE   1
2 2 2 2 2  4  4  TRUE   4
3 3 1 3 3  6  6 FALSE   6
4 4 2 4 4  8  8 FALSE   8
5 1 1 5 5 25 25  TRUE  25
6 2 2 6 6 36 36  TRUE  36
>

On Sun, Jul 19, 2009 at 5:17 PM, Mark Knecht<markknecht at gmail.com>
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)
>
> DF
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Mark Knecht
> Sent: Sunday, July 19, 2009 2:18 PM
> To: r-help
> Subject: [R] ifelse choices in a data.frame?
> 
> 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)
> 
> DF
Mark,

Why can't you use ifelse() ?

 DF$g <- with(DF, ifelse(Test,c*d,c+d))

Have I missed something in what you are doing?

Dan

Daniel Nordlund
Bothell, WA USA