Thanks Bill and David! John
----- Original Message ----- From: William Dunlap <wdun...@tibco.com> To: array chip <arrayprof...@yahoo.com>; "r-help@r-project.org" <r-help@r-project.org> Cc: Sent: Monday, August 29, 2011 5:21 PM Subject: RE: [R] weird apply() behavior apply() should come with a big warning that it was written for matrices and can cause a lot of surprises with data.frames. apply(X, ...) converts X to a matrix and that is the kernel of your problem: if any columns of X are not numeric then as.matrix(X) is a character matrix whose columns are made with calls to format(), which means that all entries in the column have the same number of characters in them. This is handy for printing but not for other purposes. > as.matrix(y) a b [1,] " 1" "2k" [2,] NA "0" > as.matrix(y[1,]) a b 1 "1" "2k" > as.matrix(y[2,]) a b 2 NA "0" Another way to debug this on your own is to simplify the function you are giving to apply. Then you would see where things are going wrong (but perhaps not why): > apply(y, 1, function(x)unlist(x)) [,1] [,2] a " 1" NA b "2k" "0" > apply(y[1,], 1, function(x)unlist(x)) 1 a "1" b "2k" > apply(y[2,], 1, function(x)unlist(x)) 2 a NA b "0" Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf Of array chip > Sent: Monday, August 29, 2011 5:03 PM > To: r-help@r-project.org > Subject: [R] weird apply() behavior > > Hi, I had a weird results from using apply(). Here is an simple example: > > > y<-data.frame(list(a=c(1,NA),b=c('2k','0'))) > > y > > a b > 1 1 2k > 2 NA 0 > > > apply(y,1,function(x){x<-unlist(x); if (!is.na(x[2]) & x[2]=='2k' & > > !is.na(x[1]) & x[1]=='1') 1 else > 0} ) > > This should print "1 0" as output, as demonstrated by: > > > apply(y[1,],1,function(x){x<-unlist(x); if (!is.na(x[2]) & x[2]=='2k' & > > !is.na(x[1]) & x[1]=='1') 1 > else 0} ) > 1 > 1 > > apply(y[2,],1,function(x){x<-unlist(x); if (!is.na(x[2]) & x[2]=='2k' & > > !is.na(x[1]) & x[1]=='1') 1 > else 0} ) > 2 > 0 > > > But it actually prints: > > > apply(y,1,function(x){x<-unlist(x); if (!is.na(x[2]) & x[2]=='2k' & > > !is.na(x[1]) & x[1]=='1') 1 else > 0} ) > > [1] 0 0 > > > Anyone has any suggestion? > > Thanks > > John > > > ______________________________________________ > 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.
