thanks for your correction Gavin. i read ?data.matrix and neglected to
pay attention to the last line of the description:
"Factors and ordered factors are replaced by their internal codes".
On Mon, Jun 16, 2008 at 5:30 PM, Gavin Simpson wrote:
On Mon, 2008-06-16 at 15:35 -0500, [EMAIL PROTECTED] wrote:
hi: you can do below but i don't know if it's worth it ?
newx <- data.matrix(data.frame(x))
print(newx)
That doesn't work Mark:
str(data.frame(x))
'data.frame': 2 obs. of 2 variables:
$ X1: Factor w/ 2 levels "1","2": 1 2
$ X2: Factor w/ 2 levels "3","4": 1 2
data.matrix(data.frame(x))
X1 X2
[1,] 1 1
[2,] 2 2
Which is as per documentation - the data.frame() coerces to factors
and
data.matrix represents factor by their internal values.
One "solution" might be to save the dims and then reapply:
mat
[,1] [,2]
[1,] "1" "3" [2,] "2" "4"
dims <- dim(mat)
mat2 <- as.numeric(mat)
dim(mat) <- dims
mat2
[,1] [,2]
[1,] 1 3
[2,] 2 4
You could wrap this in a function:
asMatrix <- function(x, ...) {
dims <- dim(x)
x <- as.double(x)
dim(x) <- dims
return(x)
}
It would be logical to define a method for as.double for matrix
objects.
However objects of class "matrix" are not objects in the sense of
isObject() and hence method dispatch will not work in this case.
HTH
G
On Mon, Jun 16, 2008 at 4:22 PM, Alberto Monteiro wrote:
Why does as.numeric convert matrices and arrays to vectors?
as.numeric(matrix(c("1", "2", "3", "4"), 2, 2))
[1] 1 2 3 4
I could only figure out ugly ways to bypass this, like:
x <- matrix(c("1", "2", "3", "4"), 2, 2)
array(as.numeric(x), dim = dim(x), dimnames = dimnames(x))
Alberto Monteiro
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Dr. Gavin Simpson [t] +44 (0)20 7679 0522
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