On May 22, 2011, at 3:22 PM, Jeroen Ooms wrote:
apply() operates on arrays and a data frame will be coerced to a
matrix
(which requires all elements to be of the same type). This is
documented in
?apply.
Thanks, I was not aware of that. I implicitly assumed there would be a
specific apply.data.frame.
Because there is a constraint in R that all elements of a vector
need to be of the same type.
This may not be elegant, but why not just use a loop:
The thing is that were are going to use this operation on a (very)
large
scale in a production environment, on datasets for which nrow >>
ncol. So I
would like the most efficient solution and if possibly, avoid
looping over
the rows.
But `apply` loops over rows, too. No speed advantage is being gained.
You may get better answers if you post a representative example that
has types on which you will be operating. There may be vectorizable
solutions that can operate column-wise.
Thanks
--
David Winsemius, MD
West Hartford, CT
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