There are various ways to do this in R.
# sample data
dd <- data.frame(a=1:10,b=sample(3,10,replace=T),c=sample(3,10,replace=T))
Using the standard built-in functions, you can use:
*** aggregate ***
aggregate(dd,list(b=dd$b,c=dd$c),sum)
b c a b c
1 1 1 10 2 2
2 2 1 3 2 1
....
*** tapply ***
tapply(dd$a,interaction(dd$b,dd$c),sum)
1.1 2.1 3.1 1.2 2.2 3.2 1.3
2.3
5.000000 3.000000 10.000000 5.000000 NA NA 5.000000
...
But the nicest way is probably to use the plyr package:
> library(plyr)
> ddply(dd,~b+c,sum)
b c V1
1 1 1 14
2 2 1 6
....
********
Unfortunately, none of these approaches allows you do return more than one
result from the function, so you'll need to write
> ddply(dd,~b+c,length) # count
> ddply(dd,~b+c,sum)
> ddply(dd,~b+c,mean) # arithmetic average
There is an 'each' function in plyr, but it doesn't seem to be compatible
with ddply.
-s
On Mon, Apr 6, 2009 at 5:37 AM, calpeda <mauro.bias...@calpeda.it> wrote:
>
> Hi,
> I ve been searching a lot in internet..but I can t find a solution
> Attached, you find a file.
> I need for each (Materiale, tpdv, UM) to find sum,avg and count
> My idea was to aggregate for the 3 parameters ..but I don t know how to get
> the numeric value (SUM,COUNT,AVG) I need.
> Can you help me?
> thank you
>
> http://www.nabble.com/file/p22905322/ordini2008_ex.txt ordini2008_ex.txt
> --
> View this message in context:
> http://www.nabble.com/SUM%2CCOUNT%2CAVG-tp22905322p22905322.html
> Sent from the R help mailing list archive at Nabble.com.
>
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