[R] How to apply functions across columns?

[R. Michael Weylandt]

Indeed, apply is very flexible and idiomatically R (i.e., the right
way to do it) -- but, just a heads up, for datasets with many
rows/columns rowMeans and colMeans will be *much* faster (there's loop
overhead in the apply family)

Best,
Michael

On Wed, May 9, 2012 at 3:46 PM, Robert Latest <boblatest at gmail.com> wrote:
> On Wed, May 9, 2012 at 4:19 PM, R. Michael Weylandt
> <michael.weylandt at gmail.com> wrote:
>> Good reproducible example ;-)
>>
>> Easiest is probably just:
>>
>> cbind(tencor, ThisRowMean =  rowMeans(tencor[, 4:8]))
>
> Actually, after frying my brain on tapply() and sapply() I found that
> just plain apply() does what I need:
>
> tencor$mean <- apply(tencor[4:8], 1, FUN=mean)
>
> This way I'm also not tied to just mean() as aggregator but can use
> any homemade function (this would have been my followup question had I
> followed your advice ;-)
>
> Thanks!
> robert
>
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