On Nov 11, 2007 11:23 AM, David Winsemius <[EMAIL PROTECTED]> wrote: > It worked. But this student of R is left wondering why or how. In > particular the construction <foo>[.][.] was puzzling. I doubt that > matters greatly, but I am using R in both a Mac (OSX 10.2 v 2.0.1) and > WinXP (v 2.4.1.) > > I have broken it into what I think are its pieces: > > table(my.mat)[-1] > my.mat > 1 2 > 9 4 > # a count of the non-zero elements > > table(my.mat)[-1][my.mat] > my.mat > 1 1 1 1 1 1 1 1 1 2 2 2 2 > 9 9 9 9 9 9 9 9 9 4 4 4 4 > > I am having some trouble figuring out how the second index, the matrix, > my.mat, is being handled by the table object ... if that is what is > happening after the semantic parsing.
foo[x][y] is not a special construct. Its just [y] applied to the result of foo[x]. table(my.mat)[-1][my.mat] is the same as (table(my.mat)[-1])[my.mat] or: tmp <- table(my.mat)[-1] tmp[my.mat] The [-1] removes the first component, i.e. the one that corresponds to 0, so that only the ones corresponding to 1 and 2 are left. Then we index that one by my.mat. Those components of my.mat that are 0 do not produce anything in the output leaving the indexing by 1 and 2 as the only ones left. The solution was specific to the fact that 0, 1 and 2 were used but a more general solution that allows gaps between the numbers would be the following (where we have used mm in place of my.mat) : mm[] <- table(mm)[factor(mm)] * c(mm > 0) > > I have searched for material on "subscripting" and found a rather small > amount, but after looking the help file, I see that I should have been > looking for "indexing" and "Extract". It appears that "[.]" is an > operation that is represented internally by Extract(.) and Extract both > extracts and replaces. > > Most of the discussions of "recursive indexing" I found were directed at > the "[[" operation, but is this construct also recursive indexing? > > -- > Sincerely; > David Winsemius > > > Gabor Grothendieck wrote: > > Try this: > > > > my.mat[my.mat > 0] <- table(my.mat)[-1][my.mat] > > > > > > On Nov 10, 2007 8:19 AM, Milton Cezar Ribeiro <[EMAIL PROTECTED]> wrote: > > > >> Hi R-gurus, > >> > >> I have a matrix which looks like > >> > >> 00000000000 > >> 01110000220 > >> 01110000220 > >> 01110000000 > >> 00000000000 > >> > >> As you can see we have non-zero levels 1 and 2. I would like to fill an > >> other matrix with the frequency of non-zero levels in each cell. The > >> results that I need is > >> > >> 00000000000 > >> 09990000440 > >> 09990000440 > >> 09990000000 > >> 00000000000 > >> > >> If I run the script below I can simulate the first matrix and count the > >> cells for each non-zero levels. My question is how can I fill the second > >> matrix in a easy way. > >> > >> my.mat<-matrix( > >> c(0,0,0,0,0,0,0,0,0,0,0, > >> 0,1,1,1,0,0,0,0,2,2,0, > >> 0,1,1,1,0,0,0,0,2,2,0, > >> 0,1,1,1,0,0,0,0,0,0,0, > >> 0,0,0,0,0,0,0,0,0,0,0),nrow=5,byrow=T) > >> my.mat.freq<-data.frame(table(my.mat)) > >> my.mat.freq<-subset(my.mat.freq,my.mat.freq$my.mat!=0) > >> my.mat.freq > >> > >> > >> Any idea? > >> > >> Kind regards > >> > >> Miltinho > >> > >> > >> > >> para armazenamento! > >> > >> [[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. > >> > >> > > > > ______________________________________________ > > 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. > ______________________________________________ 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.
