[R] Minimum distance

[BXC (Bendix Carstensen)]

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of 
> Williams, Michael
> Sent: Monday, April 18, 2005 1:58 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Minimum distance
> 
> 
> G'day, I have a matrix 20000 x 500 populated with all the 
> distances between a list of airports and a list of towers. 
> What I'm having trouble doing is finding the closest airport 
> to each tower, Any help would be greatly appreciated.

Try:

( M <- matrix( rnorm( 24 ), 8, 3 ) )
rownames( M )  <- 1:8
( wh <- sweep( M, 2, apply( M, 2, min ), "==" ) )
rownames(M)[ row( wh )[wh] ] 

It works in finite time even with M of 20000 by 500 but
it breaks down if there is more than one minimum per column.

Bendix Carstensen
----------------------
Bendix Carstensen
Senior Statistician
Steno Diabetes Center
Niels Steensens Vej 2
DK-2820 Gentofte
Denmark
tel: +45 44 43 87 38
mob: +45 30 75 87 38
fax: +45 44 43 07 06
bxc at steno.dk
www.biostat.ku.dk/~bxc
----------------------
> 
> Regards,
> Michael Williams
> 
> 
> 
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