Leeds, Mark (IED) wrote: > I just noticed something by accident with R syntax that I'm sure is > correct but I don't understand it. If I have > a simple numeric vector x and I subscript it, it seems that I can then > subscript a second time with TRUE > or FALSE, sort of like a 2 dimensional array in C. Does someone know if > this is documented somewhere > Because it's neat but I never knew it existed. To me it seems like a 1 > dimensional vector should > have only one dimensional indexing ? > > x <- seq(1,10) > >>x > > [1] 1 2 3 4 5 6 7 8 9 10 > >>x[2:4][c(TRUE,FALSE,TRUE)] > > [1] 2 4 > > But, it only works for TRUE or FALSE and not numbers so I think it's not > really 2 dimensional indexing. > > x[1][2] > > [1] NA > > If someone could explain this mechanism or tell me what I should look > for in the archives, it would > be appreciated. Thanks.
x<-1:10 x1<-x[2:4] x1 x1[c(TRUE,FALSE,TRUE)] The first extraction is performed before the second. Jim ______________________________________________ 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.
