[R] cbind(NULL,zoo.object)?

[Gabor Grothendieck]

I've just committed a fix to the zoo svn repository.  You can grab it like this:

source("http://r-forge.r-project.org/plugins/scmsvn/viewcvs.php/*checkout*/pkg/R/merge.zoo.R?rev=575&root=zoo")

On Sun, Mar 15, 2009 at 2:54 AM, Ajay Shah <ajayshah at mayin.org> wrote:
> Folks,
>
> I often build up R objects starting from NULL and then repeatedly
> using rbind() or cbind(). This yields code like:
>
> a <- NULL
> for () {
>  onerow <- craft one more row
>  a <- rbind(a, onerow)
> }
>
> This works because rbind() and cbind() are forgiving when presented
> with a NULL arg: they act like nothing happened, and you get
> all.equal(x,rbind(NULL,x)) or all.equal(x,cbind(NULL,x)).
>
> This same idea is useful in building up a zoo matrix, by cbinding one
> column after another. I find this quite elegant, though I'm conscious
> that it leads to a lot of expensive memory management.
>
> This approach breaks around zoo because cbind(NULL,z) doesn't work:
>
>  > tmp <- structure(c(2.65917577210146, 1.17190441781228, 0.838363890267146,
>             -0.293979039853021, -0.132437820890186,
>              0.262002985990861,  2.16601367541420,
>              0.375245019370496,  0.0108451048014047,
>              1.56555812127923), index = structure(c(12509,
>              12510, 12513, 12514, 12515, 12516, 12521, 12524, 12528,
>              12529), class = "Date"), class = "zoo")
>  > tmp
>   2004-04-01  2004-04-02  2004-04-05  2004-04-06  2004-04-07  2004-04-08
>   2.65917577  1.17190442  0.83836389 -0.29397904 -0.13243782  0.26200299
>   2004-04-13  2004-04-16  2004-04-20  2004-04-21
>   2.16601368  0.37524502  0.01084510  1.56555812
>  > cbind(NULL,tmp)
>        12509       12510       12513       12514       12515       12516
>   2.65917577  1.17190442  0.83836389 -0.29397904 -0.13243782  0.26200299
>        12521       12524       12528       12529
>   2.16601368  0.37524502  0.01084510  1.56555812
>  Warning message:
>  In merge.zoo(..., all = all, fill = fill, suffixes = suffixes, retclass = "zoo") :
>    Index vectors are of different classes: integer Date
>
> Is there an easy workaround; or am I deeply confused; is there a way
> out? :-)
>
> --
> Ajay Shah                                      http://www.mayin.org/ajayshah
> ajayshah at mayin.org                             http://ajayshahblog.blogspot.com
> <*(:-? - wizard who doesn't know the answer.
>
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