[R] lapply across using multiple columns

[Kingsford Jones]

try:

dfr <- data.frame(A=rnorm(50), B=runif(50),
    X=factor(sample(c('L1','L2'),50,repl=TRUE)))

by(dfr[, 1:2], dfr$X, mean)

hth,

Kingsford Jones


On Tue, Jun 23, 2009 at 7:57 PM, R_help Help<rhelpacc at gmail.com> wrote:
> Hi,
>
> To set a simple an clear picture of what I'd like to do, here is an example.
> I would like to calculate mean of column A and B bucketed by factor in
> column X in a data.frame. lapply or aggregate operates on a single column. I
> found dapply function in some package which doesn't seem to exist any more.
>
> Is there anyway that I can accomplish something like this? Thank you so much
> in advance.
>
> adschai
>
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