Does SQL group by have a heavy duty equivalent in R

I converted the whole data frame to character by using
as.matrix

And then using a posting that explained how to get the naming conventions 
back (which had been lost when converting to matrix)

Anything that I did not list with the id's it insisted in including them 
with the measured variables. In other words it would not let me drop.

despite

melted<-melt(BigDF, id=c("SAMPLE_ID","ASSAY_ID"), 
measured=c("GENOTYPE_ID","DESCRIPTION"))

unique(melted$variable)
 [1] CUSTOMER       PROJECT        PLATE          EXPERIMENT     CHIP 
WELL_POSITION  GENOTYPE_ID    DESCRIPTION    ENTRY_OPERATOR
[10] INTERACT       PLATEc
Levels: CUSTOMER PROJECT PLATE EXPERIMENT CHIP WELL_POSITION GENOTYPE_ID 
DESCRIPTION ENTRY_OPERATOR INTERACT PLATEc


I should have only got GENOTYPE_ID    and DESCRIPTION

"hadley wickham" <h.wickham at gmail.com> wrote in message 
news:f8e6ff050612310758p11f96c0dl256ac5b15d11dc2c at mail.gmail.com...

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

______________________________________________
R-help at stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.