From: Michael Rennie <mdrennie_at_gmail.com>

Date: Tue, 15 Jul 2008 09:07:09 -0400

Date: Tue, 15 Jul 2008 09:07:09 -0400

Does anyone have any tips for extracting chunks of data from a distance matrix?

############## # ex_dist.R # example for # manipulating # distance matrices ####################

set.seed<-12345

a<-sample(20:40, 10) b<-sample(80:100, 10) c<-sample(0:40, 10)

dat<-data.frame(a,b,c)

dat

dmat<-dist(dat, method="euclidean")

dmat

dmat[1:6] #vector that stores the distance matrix runs descending down columns, left to right

#in a 10-element distance matrix, column lengths are 9,8,7,6....1

#get comparisons of rows 1:4 (from dat) ONLY #top-left matrix will consist of top 3 of first column, top 2 of second col, top 1 or third col.

topleft<-c(dmat[1:3],dmat[10:11],dmat[18]) topleft

#get comparisons of rows 9:10 (from dat) ONLY #bottom right 4

bottomright<-c(dmat[8:9],dmat[16:17])

bottomright

#######end#####

I'm sure there's a simpler way to do this using the labels of the distance matrix, but I can't see it. I've thought of converting it using as.matrix(), which would allow me to pull out particular rows, but I'm only interested in the triangluar matrix. Now, if there was a way to as.matrix(dmat) such that I got the bottom triangular matrix and zeros elsewhere, then I'd be in buisness. Any suggestions on how to pull that off would be helpful.

I'm certainly interested in any tips or tricks anyone might have for working with distance matrices, or any material that people can point me towards.

Cheers,

Mike

-- Michael D. Rennie Ph.D. Candidate University of Toronto at Mississauga 3359 Missisagua Rd. N. Mississauga, ON L5L 1C6 Ph: 905-828-5452 Fax: 905-828-3792 www.utm.utoronto.ca/~w3rennie ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Tue 15 Jul 2008 - 13:26:00 GMT

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