[R] simple if question

[David Winsemius]

On Mar 26, 2011, at 7:05 PM, Sebastián Daza wrote:

> Hi everyone,
> I have just got different samples from a dataframe (independent and  
> exclusive, there aren't common elements among them). I want to  
> create a variable that indicate the sampling selection of the  
> elements in the original dataframe (for example, 0 = no selected, 1=  
> sample 1, 2=sample 2, etc.).
>
> I have tried to do it with ifelse command, but the problem is that  
> the second line replaces the values of the first line, and I haven't  
> been able to do it with the if command (I got this error: In if (data 
> $school %in% sample1) { :
>  the condition has length > 1 and only the first element will be used)
>

Nested ifelse's should work. There may be a limit to nested depth.

data$selection <- ifelse(data$school %in% sample1, 1,   # else
                      ifelse(data$school %in% sample2, 2, #else
                                                       0) )

>
> Any ideas?
> Thank you in advance.
>
> -- 
> Sebastián Daza
> sebastian.daza at gmail.com
>
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David Winsemius, MD
West Hartford, CT