R: how to get row and column names of the true elements of a matrix?

Question

I have a logical matrix x with named rows (\'a\' and \'b\') and named columns (\'10\', \'20\', \'30\', \'40\'). Let\'s say, this:

   10   20   3         


        

Answer 1

You can directly use apply.

apply(
  x, 1, 
  function(u) paste( names(which(u)), collapse="," ) 
)