I've tried and give up. I have a matrix of say 200 columns and 400 rows. For each odd ( or even i suppose if i wanted to )column, I want to know the number of rows in which the value is greater than zero. So, I did sapply(tempMatrix,2,function(x) sum( x > 0 )) this almost works but i don't know how to tell it to only do the odd columns. my guess is , like everything else in R, this is possible. Thanks.
sapply() is not the right tool. It operates on a list, and a matrix is not a list (at least not treated as you'd expected it to be). It would have sort of worked if tempMatrix were a data frame instead of a matrix. Try something like: colSums(tempMatrix[, seq(1, ncol(tempMatrix), by=2)] > 0) Andy From: markleeds at verizon.net> > I've tried and give up. I have a matrix of say 200 columns > and 400 rows. > > For each odd ( or even i suppose if i wanted to )column, I > want to know the number of rows in which the value is greater > than zero. > > So, I did sapply(tempMatrix,2,function(x) sum( x > 0 )) > > this almost works but i don't know how to tell it to only do > the odd columns. my guess is , like everything else in R, > this is possible. Thanks. > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > >
Hi Could you use something along the lines of the following: transposedat<-t(dat) transposedat$oddrow<-(1:ncol(dat))%%2 oddcolumns<-t(transposedat[transposedat$oddrow==1,]) Now you should have the odd columns in a single dataframe. gzero<-matrix(oddcolumns>0,nrow=nrow(oddcolumns),ncol=ncol(oddcolumns)) colSums(gzero) Best regards Per Jensen On 6/20/06, markleeds@verizon.net <markleeds@verizon.net> wrote:> > I've tried and give up. I have a matrix of say 200 columns and 400 rows. > > For each odd ( or even i suppose if i wanted to )column, > I want to know the number of rows in which the value is greater than zero. > > So, I did sapply(tempMatrix,2,function(x) sum( x > 0 )) > > this almost works but i don't know how to tell > it to only do the odd columns. my guess is , like everything else > in R, this is possible. Thanks. > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html >[[alternative HTML version deleted]]