[R] elegant way to check if 2 values are in 3 columns?

[David Winsemius]

On Aug 26, 2011, at 10:16 AM, Joanne Demmler wrote:

> Dear all,
>
> I'm trying to rerun some data linkage exercises in R (they are  
> designed to be done in SPSS, SAS or STATA)
> The exercise in question is to relabel the column "treat" to "1", if  
> "yearsep" is smaller than 1988 and columns "proc1"-"proc3" contain  
> the values 56.36 or 59.81.
>
> My pathetic solution to do this in R currently looks like this:
>
> vaslinks4$treat <- 0

Why not just?

   # skip the setting to 0 step
   vaslinks4$treat <- as.integer( with( vaslinks,
                          yearsep < 1988 &
                                (proc2 %in% c(56.36,59.81) |
                                 proc3 %in% c(56.36,59.81)  )
                                 )      )


Maybe, but watch out about testing for equality or set membership when  
using floating point numbers.

>
> vaslinks4$treat[vaslinks4$yearsep < 1988 && (vaslinks4$proc1 %in%  
> c(56.36,59.81)
>            || vaslinks4$proc2 %in% c(56.36,59.81)
>            || vaslinks4$proc3 %in% c(56.36,59.81))] <- 1

A doomed strategy. Don't use "&&" or "||' when working with vectors.

>
> But I'm sure there is a more elegant solution for this, in which I  
> would not have to call all three columns separately.



>
> Anyone?
> Yours Joanne
>
Snipped SAS and Stata code.

-- 

David Winsemius, MD
West Hartford, CT