a:b means - all the element in the vector from a to b a[,-1] means for the matrix a keep all the rows but not the last or first -can't remember column. When in doubt do what I do make a small matrix and apply the command see what it does. After this: > a=matrix(c(1:9),3,3) > a[,-1] [,1] [,2] [1,] 4 7 [2,] 5 8 [3,] 6 9
you see that -1 eliminates the first column. I found the R manual useless myself. The only thing useful is the search function in the html help. That has examples. Ionut Florescu Michael wrote: > Hi all, > > R is so difficult. I am so desperate. > > What does the ":" mean in the following statement? > > What does the "[, -1]" mean? > > >> # Leaps takes a design matrix as argument: throw away the intercept >> # column or leaps will complain >> >> X <- model.matrix(lm(V ~ I + D + W +G:I + P + N, election.table))[,-1] >> > > Thanks a lot! > > [[alternative HTML version deleted]] > > ______________________________________________ > 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 > > ______________________________________________ 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