I want a list of the number of times some factor levels appear together, similar to the following SQL statement: SELECT A, B, COUNT(C) FROM TBL GROUP BY A, B How do I do that with a data.frame in R? Thanks, Jesper Frickmann Statistician, Quality Control Novozymes North America Inc. 77 Perry Chapel Church Road Franklinton, NC 27525 USA Tel. +1 919 494 3266 [[alternative HTML version deleted]]
You might want to look at ?table and ?xtab. See also ?tapply for use of general functions (other than just COUNT) with GROUP BY. HTH, Vadim> -----Original Message----- > From: JFRI (Jesper Frickmann) [mailto:jfri at novozymes.com] > Sent: Friday, April 02, 2004 1:06 PM > To: r-help at stat.math.ethz.ch > Subject: [R] Doing SQL GROUP BY in R > > > I want a list of the number of times some factor levels > appear together, similar to the following SQL statement: > > SELECT A, B, COUNT(C) FROM TBL GROUP BY A, B > > How do I do that with a data.frame in R? > > Thanks, > Jesper Frickmann > Statistician, Quality Control > Novozymes North America Inc. > 77 Perry Chapel Church Road > Franklinton, NC 27525 > USA > Tel. +1 919 494 3266 > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://www.stat.math.ethz.ch/mailman/listinfo> /r-help > PLEASE > do read the posting guide! > http://www.R-project.org/posting-guide.html >
Assuming you have a data.frame, dat, with coluns A and B, I think what you want would be: > table(paste(dat$A,dat$B)) JFRI (Jesper Frickmann) wrote:> I want a list of the number of times some factor levels appear together, > similar to the following SQL statement: > > SELECT A, B, COUNT(C) FROM TBL GROUP BY A, B > > How do I do that with a data.frame in R? > > Thanks, > Jesper Frickmann > Statistician, Quality Control > Novozymes North America Inc. > 77 Perry Chapel Church Road > Franklinton, NC 27525 > USA > Tel. +1 919 494 3266 > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html >-- ----------------------------------------------------------------- Pierre Kleiber, Ph.D Email: pkleiber at honlab.nmfs.hawaii.edu Fishery Biologist Tel: 808 983-5399/737-7544 NOAA FISHERIES - Honolulu Laboratory Fax: 808 983-2902 2570 Dole St., Honolulu, HI 96822-2396 ----------------------------------------------------------------- "God could have told Moses about galaxies and mitochondria and all. But behold... It was good enough for government work."
JFRI (Jesper Frickmann) wrote:>I want a list of the number of times some factor levels appear together, > >Say a and b are the names of the factors: table(a,b) table(a:b) aggregate(a,list(a=a,b=b),length) Christophe Pallier http://www.pallier.org