This is a good example to compare different approaches. My understanding is
aggregate() can apply one function to multiple columns summarize() can apply multiple functions to one column I am not sure if ddply() can actually apply multiple functions to multiple columns? This is what I would like to do. The syntax in the help is a little confusing to me. Appreciate more comments. Thanks Jun On Mon, Apr 6, 2009 at 9:51 AM, Stavros Macrakis <macra...@alum.mit.edu>wrote: > Actually, ddply does this perfectly ... I had made a mistake in using > 'each'. The correct code is: > > ddply(dd,~b+c,function(x)each(count=length,sum=sum,avg=mean)(x$a)) > > b c count sum avg > 1 1 1 2 10 5.000000 > 2 2 1 1 3 3.000000 > 3 3 1 1 10 10.000000 > 4 1 2 2 10 5.000000 > 5 1 3 1 5 5.000000 > 6 3 3 3 17 5.666667 > > Hope this helps, > > -s > > > > On Mon, Apr 6, 2009 at 10:34 AM, Stavros Macrakis <macra...@alum.mit.edu > >wrote: > > > There are various ways to do this in R. > > > > # sample data > > dd <- > data.frame(a=1:10,b=sample(3,10,replace=T),c=sample(3,10,replace=T)) > > > > Using the standard built-in functions, you can use: > > > > *** aggregate *** > > > > aggregate(dd,list(b=dd$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.txtordini2008_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. > >> > >> ______________________________________________ > >> R-help@r-project.org 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. > >> > > > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org 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. > -- Jun Shen PhD PK/PD Scientist BioPharma Services Millipore Corporation 15 Research Park Dr. St Charles, MO 63304 Direct: 636-720-1589 [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org 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.
