[R] 'Date' elements within a matrix

[Bogaso Christofer]

Thanks everyone for clarifying my query. However I was wondering why that
Date character is not preserved within a matrix? Why R forcefully changes
that to numeric? I am especially concerned because as per the definition of
the matrix, each element needs to be of same class. Is there any other
example other than Date class which R forcefully changes to some simpler
class if it placed within a matrix?

Thanks and regards,


-----Original Message-----
From: Gabor Grothendieck [mailto:ggrothendieck at gmail.com] 
Sent: 12 March 2011 02:46
To: Bogaso Christofer
Cc: r-help at r-project.org
Subject: Re: [R] 'Date' elements within a matrix

On Fri, Mar 11, 2011 at 4:15 PM, Bogaso Christofer
<bogaso.christofer at gmail.com> wrote:
> Dear all, when I put date objects (class of 'Date') in a matrix it 
> becomes
> numeric:
>
>> dat <- matrix(seq(as.Date("2011-01-01"), as.Date("2011-01-09"), by="1
> day"), 3)
>
>> dat
>
>      [,1]  [,2]  [,3]
>
> [1,] 14975 14978 14981
>
> [2,] 14976 14979 14982
>
> [3,] 14977 14980 14983
>
>> class(dat[1,1])
>
> [1] "numeric"
>
>
>
> As it could not preserve the 'Date' characteristics after putting my 
> Date observations, I find it difficult to carry forward further 
> calculation with Dates. Can somebody help me on how to preserve the 
> Data properties while storing them within some matrix?

If its important to you to store them in a matrix (as opposed to a data
frame) then try storing them in a matrix of lists:

> dd <- seq(as.Date("2011-01-01"), as.Date("2011-01-09"), by = "day") m 
> <- matrix(as.list(dd), 3) m[[1,1]]
[1] "2011-01-01"


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