# Re: [R] Annoyance in as.numeric

From: <markleeds_at_verizon.net>
Date: Mon, 16 Jun 2008 17:00:26 -0500 (CDT)

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, markleeds@verizon.net 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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>>
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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Mon 16 Jun 2008 - 22:22:18 GMT

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