search for: idx4b

Dear R, I found a very wired behavior for a 2-by-2 matrix, see this example > A <- matrix(1:4, 2) > idx4A <- matrix(1:4, 2) > A[idx4A] Error in A[idx4A] : subscript out of bounds But other matrices are fine, > B <- matrix(1:9, 3) > idx4B <- matrix(1:9, 3) > B[idx4B] [1] 1 2 3 4 5 6 7 8 9 I can reproduce this for both 32bit windows and 64bit linux with R 2.12.1 and some earlier versions. Can someone tell me whether this a bug or a feature or something I don't know? Thanks! Feng -- Feng Li Department of Statistics St...

...o A, and two rows to idx4A, then this > form is used. > The first row of idx4A is c(1, 3) so the first value extracted is > A[1, 3] > which doesn't exist, thus the error message. > > > But other matrices are fine, > > > >> B <- matrix(1:9, 3) > >> idx4B <- matrix(1:9, 3) > >> B[idx4B] > > [1] 1 2 3 4 5 6 7 8 9 > > The part that surprises me is that this works. > Apparently there is an implicit conversion to vector here because > dim(B) != ncol(idx4B) > > What you seem to want is > A[as.vector(idx4A)] > and...