Sort matrix by column 1 ascending then by column 2 decending

Try this:

cbind(sort(x[,1]), unlist(tapply(x[,2], x[,1], sort, decreasing = T)))

On Wed, May 27, 2009 at 9:39 AM, Paul Geeleher <paulgeeleher at gmail.com>
wrote:

I've got a matrix with 2 columns and n rows. I need to sort it first
by the values in column 1 ascending. Then for values which are the
same in column 1, sort by column 2 decending. For example:

2 .5
1 .3
1 .5
3 .2

Goes to:

1 .5
1 .3
2 .5
3 .2

This is easy to do in spreadsheet programs but I can't seem to work
out how to do it in R and haven't been able to find a solution
anywhere.


Thanks!

-Paul.

--
Paul Geeleher
School of Mathematics, Statistics and Applied Mathematics
National University of Ireland
Galway
Ireland

--
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

I've got a matrix with 2 columns and n rows. I need to sort it first
by the values in column 1 ascending. Then for values which are the
same in column 1, sort by column 2 decending. For example:

2 .5
1 .3
1 .5
3 .2

Goes to:

1 .5
1 .3
2 .5
3 .2

This is easy to do in spreadsheet programs but I can't seem to work
out how to do it in R and haven't been able to find a solution
anywhere.


Thanks!

-Paul.