[R] How to apply a function to all combinations of the values of 2 or more variables?

[baptiste auguie]

I think you want to have a look at the plyr or doBy packages.

It would be easier to give a precise answer with a minimal example.

HTH,

baptiste

On 15 Apr 2009, at 18:03, Lane, Jim wrote:

> Hi, All
>
> Forgive me if this is a stupid newbie question. I'm having no luck
> googling an answer to this, probably because I don't know the right R
> terminology to frame my question. I want to know how to run an R
> function on each combination of the values of 2 or more variables. In
> SAS-speak this is multiple "BY variables" or "CLASS variables".
>
> In R I've figured out how to do what I want with one by value.
>
> by(mf,mf$centre,summary)
>
> Centre is one of the columns in the data frame "mf" which looks like
> this:
>
> names(mf)
> [1] "centre"   "complex"  "appl"     "pool"     "month"    "alloc_gb"
>
> I'd like to analyze, for example, by complex within centre. This has a
> manageable number of combinations:
>
> table(mf$centre,mf$complex)
>
>                   A      B      C      D      E      F      G      H
> I      J      K      L
>  B         0      0      0      0      0      0      0      0      0
> 0      0  60574      0
>  G        44    209      0  94613      0    156      0   2541      0
> 748      0      0 215511
>  O         0      0      0      0      0      0   3446      0    676
> 0  84400      0      0
>  Q         0      0    298      0  66277      0      0      0      0
> 0      0      0      0
>
> In SAS what I'm after is something like:
>
> Proc summary nway;
> class centre complex;
> var alloc_gb;
> output out=s sum=;
> run;
>
> How do I get something similar in R?
>
> Jim Lane
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_____________________________

Baptiste Auguié

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag