Hi Daisy, You've got a conceptual problem and a couple of practical ones, I think.
On Tue, Jun 28, 2011 at 9:29 PM, Daisy Englert Duursma <daisy.duur...@gmail.com> wrote: > Hello, > > I think this is a simple problem but I am not coming up with a simple > solution. I think it just an indexing problem. > > I can easily replace values in a matrix from a dataframe when the > dataframe has row and column numbers. In the example below I use row > and column names and I can not get it to work It's not so much that a matrix has row and column numbers instead of names, as that any matrix or dataframe can be indexed numerically. > #make a matrix where rows and columns are the lat and long for a > bounding box of Australia and all elements have the value of -9990 > > bb<-matrix(c(rep(-9999,691*886)),nrow=691 > ,ncol=886,dimnames=list(seq(-10,-44.50,by=-0.05),seq(112,156.25,by=0.05))) > > #dfr with row names and col names and values to be replaced in the matrix > > dfr <- data.frame(cbind(x=seq(120,125,by=0.05), y=-25, var.1=1)) Why are you making this into a dataframe? You're ending up with y containing -25 repeated 101 times, and var.1 containing 1 repeated 101 times. If these aren't actually going to be different in your final version, I'd make a list instead. Also, x actually corresponds to the column names of bb, and y to the rownames. > #insert the values from the dfr into the matrix > bb[dfr$x,dfr$y]<-d$var.1 And then you're trying to use x and y for indexing, rather than comparing them to the names of bb. You need to use (with x and y switched): bb[rownames(bb) %in% as.character(dfr$y), colnames(bb) %in% as.character(dfr$x)] And you can assign anything you want to that, except d$var.1 because that doesn't exist. Presumably you mean dfr$var.1. Sarah -- Sarah Goslee http://www.functionaldiversity.org ______________________________________________ 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.
