Thank you, Arun and Sarah I was not trying to "take row 0 that does not exist", rather trying "not to take" (I wrote "TM[- unused.rows,]") something that does not exist.
So what I understand from Arun's answer is that I was badly using MINUS with a vector instead of NOT with a logical. Olivier -----Message d'origine----- De : arun [mailto:smartpink...@yahoo.com] Envoyé : jeudi 13 mars 2014 16:13 À : r-help@r-project.org Cc : Olivier ETERRADOSSI Objet : Re: [R] behaviour of rows and colomns suppression in a matrix Hi, You could use: TM2[!margin.Rows <=thresh,!margin.Cols <=thresh] # [,1] [,2] #[1,] 1 1 #[2,] 1 1 #[3,] 1 1 #For the first case: TM1[!margin.Rows <=thresh,!margin.Cols <=thresh] # [,1] [,2] #[1,] 1 1 #[2,] 1 1 A.K. On Thursday, March 13, 2014 10:02 AM, Olivier ETERRADOSSI <olivier.eterrado...@mines-ales.fr> wrote: Hi List, while running a script on a set of matrices I came into a case I would not have guessed to arrive. Below is a small toy example to illustrate the case. Of course there is a simple workaround (using a simple test), but why does this occur, and shouldn’t it be corrected ? More probably I miss a point, but which one ? Is this behavior obtained on purpose and why ? Sorry if it’s a FAQ… I didn’t find my way to it. (And sorry for multiple posting if any : I got a warning from r-bounce but did not understand it). Thanks, Olivier ############################################# # toy example 1 (no problem with this one) toy.matrix.1<-matrix(c(1,0,1,1,0,1,0,0,0),3,3) # getting the marginal sums margin.Rows<- apply(toy.matrix.1,MARGIN=1,FUN=sum) margin.Cols<- apply(toy.matrix.1,MARGIN=2,FUN=sum) #giving a threshold for lines and columns suppression thresh<-0 # finding the items to remove unused.rows<-which(margin.Rows<=thresh) # unused.rows == 2 unused.cols<-which(margin.Cols<=thresh) # unused.cols == 3 TM1<-toy.matrix.1 TM1<-TM1[-unused.rows,] TM1<-TM1[,-unused.cols] TM1 # [,1] [,2] #[1,] 1 1 #[2,] 1 1 # OK ############################################## # toy example 2 (oops, no rows to suppress…) toy.matrix.2<-matrix(c(1,1,1,1,1,1,0,0,0),3,3) # getting the marginal sums margin.Rows<- apply(toy.matrix.2,MARGIN=1,FUN=sum) margin.Cols<- apply(toy.matrix.2,MARGIN=2,FUN=sum) #giving a threshold for lines and columns suppression thresh<-0 unused.rows<-which(margin.Rows<=thresh) # unused.rows == integer(0) unused.cols<-which(margin.Cols<=thresh) # unused.cols == 3 TM2<-toy.matrix.2 TM2<-TM2[-unused.rows,] TM2<-TM2[,-unused.cols] TM2 # [,1] [,2] # empty... ############################################### # I was expecting : # [,1] [,2] #[1,] 1 1 #[2,] 1 1 #[3,] 1 1 # which of course is obtained using : TM2<-toy.matrix.2 if(length(unused.rows) !=0) {TM2<-TM2[-unused.rows,]} if(length(unused.rows) !=0 ){TM2<-TM2[,-unused.cols]} TM2 ______________________________________________ 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.
