[R] defining columns in a matrix

[David Winsemius]

On Mar 12, 2010, at 5:29 PM, Kindra Martinenko wrote:

> Hi all,
> I have the following 7 x 7 matrix.  I am trying to figure out how to
> label the columns to something more descriptive other than [,1], [,2],
> etc.
> I have tried the c(x,y,z,) function, but I get a error returned
> stating that my vectors need to be the same length.  Do I need to
> convert this to something else such as a list and then repack it?
>
> Thanks,
> Kindra
>
>         Volume
> Time        [,1] [,2] [,3] [,4] [,5] [,6] [,7]
>  17:00:00 7146 4926 5394 4534 6273 6192 6189
>  17:10:00 7227 4851 5414 4620 6026 7159 5878
>  17:20:00 7477 4678 5502 4298 6516 6469 5631
>  17:30:00 6533 4608 4813 4212 6083 5837 5657
>  17:40:00 6355 4669 5106 4242 5717 5635 5282
>  17:50:00 5657 4472 4545 3860 5378 4804 5304
>  18:00:00 5338 4508 4273 4024 4666 4597 5162

I suspect that is a zoo object, a special sort of matrix. Your  
questions would be more clear if instead of presenting the results of  
the print command you would instead present the results of dput(object).

The answers you have gotten so far will work if it is a zoo object
 > z2 <- zoo(matrix(1:12, 4, 3), as.Date("2003-01-01") + 0:3)
 >
 > z2

2003-01-01 1 5  9
2003-01-02 2 6 10
2003-01-03 3 7 11
2003-01-04 4 8 12
 > is.matrix(z2)
[1] TRUE
 > colnames(z2) <- c("one", "two", "three")
 > z2
           one two three
2003-01-01   1   5     9
2003-01-02   2   6    10
2003-01-03   3   7    11
2003-01-04   4   8    12

 > class(z2)
[1] "zoo"

>


David Winsemius, MD
West Hartford, CT