[R] how to slice a zoo object

[Gabor Grothendieck]

On Mon, Jan 24, 2011 at 4:51 AM, Blair Sutton <blairuk at gmail.com> wrote:
> Hi
>
> Would anyone have any pointers on how to slice up a large zoo table. I
> have the following structure: -
>
>> str(ZOO_OBJ)
>  zoo [1:632, 1:83] 30.4 30.4 30.4 30.4 30.3 ...
>  - attr(*, "dimnames")=List of 2
>   ..$ : NULL
>   ..$ : chr [1:83] "COL1" "COL2" "COL3" "COL4" ...
>  - attr(*, "index")= POSIXct[1:632], format: "2009-05-01 01:00:00"
> "2009-05-02 01:00:00" ...
>
> and I would just like to take only arbitrary columns, i.e. another zoo
> object with only the columns "COL2", "COL5", etc..
>
> I've tried various syntactical combinations such as those for
> data.frames and also tried manipulating the coredata(). What would be
> nice would be the ability to do this by column names and not their
> indexes.
>
> Any help appreciated and thanks in advance,

It works the same as matrices:

> library(zoo)
> z <- zoo(cbind(A = 1:4, B = 5:8, C = 9:12))
> z[, c("A", "C")]
  A  C
1 1  9
2 2 10
3 3 11


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