[R] Selecting rows according to a column

[Adaikalavan Ramasamy]

Not very elegant but try:

  z <- data.frame(a = 1:5, b=10*(1:5), c = c("a", "a", "b", "b", "b") )
  z[ cbind( 1:nrow(z), match( as.character(z$c) , colnames(z) ) ) ]

If you have very few columns, you can use ifelse() too.

Regards, Adai



Gurpal Kalsi wrote:
> Hi,
> 
> With a data such as:
>> z = data.frame(a = 1:5, b=10*a, c = c("a", "a", "b", "b", "b") )
> * a  b  c*
>  *1* 10 *a*
>  *2* 20 *a*
>  3 *30* *b*
>  4 *40* *b*
>  5 *50* *b*
> 
> Can anyone suggest a way to select [1, 2, 30, 40, 50],
> ie. using column "c" to specify which column is selected for each row.
> 
> Many thanks
> 
> G
> 
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> 
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