ifelse worked like a charm for this newbie. Thanks, Dennis!

-Frank

On Feb 14, 2011, at 3:39 AM, Dennis Murphy wrote:

> Hi:
> 
> Wouldn't ifelse() work here?
> 
> tco <- with(df, ifelse(TargetColor == 'B', CannonOriB, CannonOriR))
> 
> ifelse() is vectorized, so there should be no need for a loop.
> 
> Test:
> > df <- data.table(TargetColor = c('B', 'R'), CannonOriB = c(5, 5),
> +                  CannonOriR = c(3, 3), stringsAsFactors = FALSE)
> > with(df, ifelse(TargetColor == 'B', CannonOriB, CannonOriR))
> [1] 5 3
> 
> HTH,
> Dennis
> 
> On Mon, Feb 14, 2011 at 1:02 AM, Frank Tamborello 
> <franklin.tambore...@uth.tmc.edu> wrote:
> Dear R-Help,
> 
> I am trying to compute a new variable, let's call it "target cannon 
> orientation (tco)" based conditionally on old variables, "TargetColor," 
> "CannonOriB," and "CannonOriR." For every case in the data set, if 
> TargetColor is "B" then I want tco to equal the value for that case of 
> CannonOirB, else CannonOriR. I've tried writing for loops and functions that 
> I can feed to sapply. I suspect there must be a simple solution but I cannot 
> seem to get either incantation to perform the assignment. What would be a 
> good way to do this?
> 
> Example data:
> TargetColor.1.18     CannonOriB.1.18     "CannonOriR.1.1
> "B"     5       3
> "R"     5       3
> 
> 
> Example assignment of tco
> "tco"
> 5
> 3
> 
> Thanks much!
> 
> Frank Tamborello, PhD
> W. M. Keck Postdoctoral Fellow
> School of Biomedical Informatics
> University of Texas Health Science Center, Houston
> https://xfiles.uth.tmc.edu/Users/ftamborello/public/index.html
> 
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