R help - Dec 2011 - Recoding multiple TRUE/FALSE columns into a single list of TRUE columns

Hi everyone,

I need to recode multiple columns in a dataframe into a single column in a
variety of different ways.  Often the values will be TRUE/FALSE and I want a
list of the columns that are true as in the Result column below:
 
    P1   P2   P3   P4   Result   
1   0    0    1    1    P3,P4
2   0    1    1    1    P2,P3,P4
3   1    0    0    0    P1
4   0    0    0    0    NA
5   1    1    1    1    P1,P2,P3,P4

I'm still relatively new to R and tend to think in for loops. I'm sure
there
exists a more concise and elegant solution. Any advice?

Happy holidays,
-david

Try this:
> x <- read.table(text = "   P1   P2   P3   P4
+ 1   0    0    1    1
+ 2   0    1    1    1
+ 3   1    0    0    0
+ 4   0    0    0    0
+ 5   1    1    1    1  ", header = TRUE)
> labs <- apply(x, 1, function(.row){
+     indx <- which(.row == 1)
+     if (length(indx) > 0) return(paste(names(x)[indx], collapse =
','))
+     else return(NA)
+ })
> x$result <- labs
> x
  P1 P2 P3 P4      result
1  0  0  1  1       P3,P4
2  0  1  1  1    P2,P3,P4
3  1  0  0  0          P1
4  0  0  0  0        <NA>
5  1  1  1  1 P1,P2,P3,P4
>

On Sun, Dec 25, 2011 at 7:30 PM, David Epstein <davideps at umich.edu>
wrote:
> Hi everyone,
>
> I need to recode multiple columns in a dataframe into a single column in a
> variety of different ways. ?Often the values will be TRUE/FALSE and I want
a
> list of the columns that are true as in the Result column below:
>
> ? ?P1 ? P2 ? P3 ? P4 ? Result
> 1 ? 0 ? ?0 ? ?1 ? ?1 ? ?P3,P4
> 2 ? 0 ? ?1 ? ?1 ? ?1 ? ?P2,P3,P4
> 3 ? 1 ? ?0 ? ?0 ? ?0 ? ?P1
> 4 ? 0 ? ?0 ? ?0 ? ?0 ? ?NA
> 5 ? 1 ? ?1 ? ?1 ? ?1 ? ?P1,P2,P3,P4
>
> I'm still relatively new to R and tend to think in for loops. I'm
sure there
> exists a more concise and elegant solution. Any advice?
>
> Happy holidays,
> -david
>
> ______________________________________________
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-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.

Jim,

Wow, that does it! I think I can use strsplit and unlist 
to convert the string of row names into a R list.

thank you!

-david