Bug in "[<-.matrix"? (Was: Feature Request: "matrix[1:10,1:10, block=F] <- 1:10")
On Wed, 20 Feb 2002, Warnes, Gregory R wrote:
Thanks to David Meyer [david.meyer@ci.tuwien.ac.at] and David Brahm [brahm@alum.mit.edu] who suggested: m[ cbind(index.i, index.j) ] <- vals This works fine for the example I gave. Unfortunately, this approach doesn't extend to using the row and column names to make assignments:
m <- matrix("",ncol=3,nrow=3)
dimnames(m) <- list(c("a","b","c"), c("A","B","C"))
m
A B C a "" "" "" b "" "" "" c "" "" ""
index.i <- c("b","a","c")
index.j <- c("B","A","C")
vals <- c("1","2","3")
m[ cbind(index.i, index.j) ] <- vals
m
b a c B A C "" "" "" "" "" "" "" "" "" "1" "2" "3" "1" "2" "3" This looks like a bug...
It's as documented. Take a look at e.g. the description of indexing in Venables & Ripley. You can use match() to turn names into numbers.
From the R Language Definition:
It is possible to use a matrix of integers as an index ... S throws an error in your example, and perhaps R should too. But not giving errors when used in undocumented ways is not a bug.
Brian D. Ripley, ripley@stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272860 (secr) Oxford OX1 3TG, UK Fax: +44 1865 272595 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-devel mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-devel-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._