[R] grouped colSums without for loops?

[Albert Greinoecker]

try:
aggregate(d[,2:3], by=list(d$foo), FUN=sum)

cheers,
Albert

Am Dienstag, den 18.03.2008, 11:41 +0100 schrieb Hans Ekbrand:
> Consider the following data.frame, d.
> 
> d <- data.frame(c("a","b","c","d","b","a"), c(1,4,85,3,4,1), c(7,6,2,4,15,33))
> names(d) <- c("foo", "bar", "baz")
>  
> To get the colsum of d[[2]] for the rows that have d$foo == "a" I know
> I can use
> 
> colSums(subset(d, d[[1]] == "a", select = 2))
> 
> But what is needed to get a list of colSums for d[[2]] for each factor
> of d$foo ? Can it be done without a for loop?
> 
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