R help - Oct 2011 - Summary stats in table

Suppose I have data like this:

A <- sample(letters[1:3], 1000, replace=TRUE)
B <- sample(LETTERS[1:2], 1000, replace=TRUE)
x <- rnorm(1000)

I can get a table of means via

tapply(x, list(A, B), mean)

and I can add the marginal means to this using cbind/rbind:

main <- tapply(x, list(A,B), mean)
Amargin <- tapply(x, list(A), mean)
Bmargin <- tapply(x, list(B), mean)

rbind(cbind(main, all=Amargin),all=c(Bmargin, mean(x)))

But this is tedious.  Has some package got some code that makes this easier?

Duncan Murdoch

I had to set it up as a data frame and then it workd beautifully with the
reshape package.
 
DF<-data.frame(A,B,x)
library(reshape)

cast(DF, A ~ B, fun.aggregate=mean, 
     margins=c("grand_row", "grand_col"))
 
Cheers
Tyler
----------------------------------------
> Date: Sun, 23 Oct 2011 14:39:08 -0400
> From: murdoch.duncan at gmail.com
> To: R-help at r-project.org
> Subject: [R] Summary stats in table
>
> Suppose I have data like this:
>
> A <- sample(letters[1:3], 1000, replace=TRUE)
> B <- sample(LETTERS[1:2], 1000, replace=TRUE)
> x <- rnorm(1000)
>
> I can get a table of means via
>
> tapply(x, list(A, B), mean)
>
> and I can add the marginal means to this using cbind/rbind:
>
> main <- tapply(x, list(A,B), mean)
> Amargin <- tapply(x, list(A), mean)
> Bmargin <- tapply(x, list(B), mean)
>
> rbind(cbind(main, all=Amargin),all=c(Bmargin, mean(x)))
>
> But this is tedious. Has some package got some code that makes this easier?
>
> Duncan Murdoch
>
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.

On Mon, Oct 24, 2011 at 5:39 AM, Duncan Murdoch
<murdoch.duncan at gmail.com> wrote:
> Suppose I have data like this:
>
> A <- sample(letters[1:3], 1000, replace=TRUE)
> B <- sample(LETTERS[1:2], 1000, replace=TRUE)
> x <- rnorm(1000)
>
> I can get a table of means via
>
> tapply(x, list(A, B), mean)
>
> and I can add the marginal means to this using cbind/rbind:
>
> main <- tapply(x, list(A,B), mean)
> Amargin <- tapply(x, list(A), mean)
> Bmargin <- tapply(x, list(B), mean)
>
> rbind(cbind(main, all=Amargin),all=c(Bmargin, mean(x)))
>
> But this is tedious. ?Has some package got some code that makes this
easier?
Have a look at reshape2::add_margins - it's not super efficient, but I
think cool because it works for arbitrarily many dimensions.

Hadley

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/