[R] Sorting a matrix by a column

[Prof Brian Ripley]

On Mon, 4 Aug 2008, John Sorkin wrote:

> R 2.6
> Windows XP
>
> I have a 100x4 matirx
>
> data<-matrix(nrow=100,ncol=4)
>
> I would like to sort the entire matrix by column two, i.e. data[,2]
> I looked at the help page for sort() but can not determine how I can use it to sort a matrix on one of the matrix's columns.

Rather, use sort.list, e.g.  data[sort.list(data[,2]), ]

There's an example for data frames on ?order.

>
> Thanks,
> John
>
> John David Sorkin M.D., Ph.D.
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
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>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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