[R] R-ish challenge for dependent ranking

[baptiste auguie]

Hi


I think you want something like,

> with(ds, tapply(yn, drank1group, rank) )

also, the reshape package should do this sort of thing neatly.

Hope this helps,

baptiste

On 25 Aug 2008, at 16:10, ivo welch wrote:

> Dear R wizards:  First, thanks for the notes on SQL.  These pointers
> will make it a lot easier to deal with large data sets.   Sorry to
> have a second short query the same day.  I have been staring at this
> for a while, but I cannot figure out how to do a dependent ranking the
> R-sh way.
>
> ds= data.frame( xn=rnorm(32), yn=rnorm(32), zn=rnorm(32) )
> ds$drank1group= as.integer((rank( ds$xn )-1)/4)  # ok, the first set
> of 8 groups, each with 4 elements
>
> ds$drank2.bydrank1group= ??? ## here I want within each drank1group
> the rank based on yn (from 1 to 4)
>
> something like "by(ds,drank1group, rank(ds$yn))".  obviously, this
> neither works nor has same dimensional output.
>
> of course, there is a really simple, clever way to do this in
> R...except that it totally eludes me.  before I start writing a hand
> iterating function, could someone please let me know how to do this?
>
> regards,
>
> /iaw
>
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_____________________________

Baptiste Auguié

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag