HI, Not sure if this is what you wanted. mat1<- matrix(c(1, 1, -1, -1, 1, -1, -1, -2, 1, 1, 1, 1), byrow=TRUE, nc=4)
fun1<- function(mat){ matP<- mat matN<- mat matP[matP<0]<- NA matN[matN>0]<- NA resP<-rowSums(matP,na.rm=TRUE)/ncol(matP) resN<- rowSums(matN,na.rm=TRUE)/ncol(matN) res<- rbind(resP,resN) row.names(res)<- c("Mean_Pos","Mean_Neg") res } fun1(mat1) # [,1] [,2] [,3] #Mean_Pos 0.5 0.25 1 #Mean_Neg -0.5 -1.00 0 A.K. hello, when i use the function rowMeans, which is sum/n, can i divide it in 2 parts, -> Sum(just positive values)/n and Sum(just negative values)/n. i need both for my regression but dont know how to do it. for example we have the matrix 1 1 -1 -1 -> rowMeans([1:3 , 2]) just positive -> 1 1 -1 -1 -2 1/2 here not 0 because we dont use the -1 1 1 1 1 1 thanks for helping ______________________________________________ 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.