Is there an easy way to build a matrix in R based on several other block matrix?
Suppose that I have A1,A2,A3 and A4 matrix. I want to construct a Matrix A that is the equivalent in matlab of [A1,A2;A3;A4]. I know that i could use rbind(cbind(A1,A2),cbind(A3,A4)), is there a more efficient and direct way?
R doesn't really have a lot of shortcut notations for creating matrices like matlab. The most explicit it just to stick with the rbind and cbind as you've already done. If it's something you find yourself doing a lot, you could write a helper function like this
mat_shape <- function(expr) {
env<-new.env(parent=parent.frame())
env[[":"]] <- base::cbind
env[["/"]] <- base::rbind
eval(substitute(expr), envir = env)
}
here we re-refine : to be cbind and / to be rbind for this particular function input. Then you could do
A <- matrix(1:6, ncol=3)
B <- matrix(1:4, ncol=2)
C <- matrix(1:3, ncol=1)
D <- matrix(1:12, ncol=4)
mat_shape(A:B/C:D)
# [,1] [,2] [,3] [,4] [,5]
# [1,] 1 3 5 1 3
# [2,] 2 4 6 2 4
# [3,] 1 1 4 7 10
# [4,] 2 2 5 8 11
# [5,] 3 3 6 9 12