Very simple question that I want to ask in a general way because it seems to be a recurrent problem, and I would be glad to find a generic way to do it. The problem is to convert a matrix of logicals, for instance, into a matrix of factors, for instance, but keeping the matrix structure: number of rows & columns, colnames, rownames. I would like something more straightforward than
X2 <- matrix(as.mode(X), ncol=ncol(X));
rownames(X2) <- rownames(X) ...
I already have figured out this problem for some cases, so I put it here, but some questions remain...
A. into (-->) factors is the one I don't have an easy way to do.
B. 1. logicals --> numeric: uses the '+0' trick
BoolMatrix <- matrix(c(TRUE,FALSE),nrow=3,ncol=2)
rownames(BoolMatrix) <- LETTERS[1:3]; colnames(BoolMatrix) <-LETTERS[11:12]
(NumMatrix <- BoolMatrix + 0)
B. 2. numeric --> logical: uses directly the condition
NumMatrix <- matrix(1:6, ncol=2)
rownames(NumMatrix) <- LETTERS[1:3]; colnames(NumMatrix) <-LETTERS[11:12]
(BoolMatrix <- NumMatrix == 0)
C. numeric <--> character: cannot do better than a 2 liner, directly changing the mode works (and would also work between logicals and numerics, but above solutions are more elegant)
CharMatrix <- NumMatrix
mode(CharMatrix) <-"character"
print(CharMatrix)
the last solution ("2 liner") works actually for anything that is not related to factors, for which I am having difficulties...
Any idea ? :-)
Use structure, which attaches a list of attributes to an arbitrary object. For a matrix, the attributes you want are dim and, optionally, dimnames.
Eg conversion of X to a matrix of factors:
m <- structure(factor(X), dim=dim(X), dimnames=dimnames(X))