How to apply functions across columns?

On Wed, May 9, 2012 at 4:19 PM, R. Michael Weylandt

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