R help - Apr 2003 - Efficiency: whole vector and for loop methods

Dear R-help,

As a generalization, is it more efficient to use a single method to 
selectively transform items in a matrix?  Preferably whole-vector, yes; but 
if one of the column vectors compels the use of a "for loop", is it
then
faster to do all of the transformations for the matrix via that "for
loop",
rather than use a mixture of methods on a column-wise basis?

TIA

graham lawrence

Based on your particular problem, you can test the efficiency of any 
method you can think of with the system.time() function. I find it 
difficult to give a better advice considering the little information you 
provided about your problem.

If that doesn't help, perhaps you could send a simple and reproducable 
example of what you want to do.

Jerome

On April 2, 2003 09:41 am, graham lawrence wrote:
> Content-Length: 535
> Status: R
> X-Status: N
>
>
> Dear R-help,
>
> As a generalization, is it more efficient to use a single method to
> selectively transform items in a matrix?  Preferably whole-vector, yes;
> but if one of the column vectors compels the use of a "for loop",
is it
> then faster to do all of the transformations for the matrix via that
> "for loop", rather than use a mixture of methods on a column-wise
basis?
>
> TIA
>
> graham lawrence
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help

On Wed, 2 Apr 2003, graham lawrence wrote:
>
> Dear R-help,
>
> As a generalization, is it more efficient to use a single method to
> selectively transform items in a matrix?  Preferably whole-vector, yes; but
> if one of the column vectors compels the use of a "for loop", is
it then
> faster to do all of the transformations for the matrix via that "for
loop",
> rather than use a mixture of methods on a column-wise basis?
>
Hard to say.

My guess is that a mixture of methods would be faster, but the only
reliable answer to 'is it faster' is to try it and see.

	-thomas