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
Capacity Planner
RBC Financial Group
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Baptiste Auguié
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University of Exeter
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