Re: [R] Does SQL group by have a heavy duty equivalent in R

From: hadley wickham <h.wickham_at_gmail.com>
Date: Sun 31 Dec 2006 - 15:58:34 GMT

> nr.attempts
> <-aggregate(RawSeq$GENOTYPE_ID,list(sample=RawSeq$SAMPLE_ID,assay=RawSeq$ASSAY_ID),length)
> This was simply to figure out how many times the same piece of information
> had been obtained. I ran out of patience. It took beyond forever and tapply
> did not perform much better. The reshape package did not help - it implied
> one was out of luck if the data was not numeric. All of my data is character
> or factor.

The reshape package will work if all your data is numeric, or all of it is character - it doesn't work with a mix. I will try and make this more clear in the documentation.
However, depending on the size and structure of your data it may not be any faster than tapply or aggregate.

Hadley



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