On May 4, 2011, at 17:52 , William Dunlap wrote: >> -----Original Message----- >> From: r-help-boun...@r-project.org >> [mailto:r-help-boun...@r-project.org] On Behalf Of Petr Savicky >> Sent: Wednesday, May 04, 2011 12:51 AM >> To: r-help@r-project.org >> Subject: Re: [R] Simple loop >> >> On Tue, May 03, 2011 at 12:04:47PM -0700, William Dunlap wrote: >> [...] >>> ave() can deal that problem: >>>> cbind(x, newCol2 = with(x, ave(H, Site, Prof, >>> FUN=function(y)y-min(y)))) >>> Site Prof H newCol2 >>> 1 1 1 24 8 >>> 2 1 1 16 0 >>> 3 1 1 67 51 >>> 4 1 2 23 0 >>> 5 1 2 56 33 >>> 6 1 2 45 22 >>> 7 2 1 67 21 >>> 8 2 1 46 0 >>> Warning message: >>> In min(y) : no non-missing arguments to min; returning Inf >>> The warning is unfortunate: ave() calls FUN even for when >>> there is no data for a particular group (Site=2, Prof=2 in this >>> case). >> >> The warning may be avoided using min(y, Inf) instead of min(). > > Yes, but the fact remains that ave() wastes time and causes > unnecessary warnings and errors by calling FUN when it knows > it will do nothing with the result (because there are no entries > in x with a given combination of the factor levels in the ... > arguments). > > Using paste(Site,Prof) when calling ave() is ugly, in that it > forces you to consider implementation details that you expect > ave() to take care of (how does paste convert various types > to strings?). It also courts errors since paste("A B", "C") > and paste("A", "B C") give the same result but represent different > Site/Prof combinations.
Well, ave() uses interaction(...) and interaction() has a "drop" argument, so > with(x, ave(H, Site, Prof, drop=TRUE, FUN=function(y)y-min(y))) [1] 8 0 51 0 33 22 21 0 (I suppose ?ave should be a bit more explicit about passing "...") > > Bill Dunlap > Spotfire, TIBCO Software > wdunlap tibco.com > >> >> cbind(x, newCol2 = with(x, ave(H, Site, Prof, >> FUN=function(y)y-min(y,Inf)))) >> >> Site Prof H newCol2 >> 1 1 1 24 8 >> 2 1 1 16 0 >> 3 1 1 67 51 >> 4 1 2 23 0 >> 5 1 2 56 33 >> 6 1 2 45 22 >> 7 2 1 67 21 >> 8 2 1 46 0 >> >> Another approach is to combine Site, Prof to a single column >> in any way suitable for the application. For example >> >> cbind(x, newCol2 = with(x, ave(H, paste(Site, Prof), >> FUN=function(y)y-min(y)))) >> >> Petr Savicky. >> >> ______________________________________________ >> 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. >> > > ______________________________________________ > 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. -- Peter Dalgaard Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.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.
