Hi >From what you write it seems to me a work for outer(). Did you try it?
Cheers Petr On 15 Nov 2004 at 22:26, Timothy W. Victor wrote: > R-List, > > I'm trying to compute pairwise distances among pairs of observations, > which each pair containing data from 2 groups. There are more than > 100000 unique pairs. I have programmed a distance function that has > three parameters, a vector of covariates from the ith observation in > Group 1, a vector of covarites from the jth observation in Group 2, > and a weighting matrix. > > I have used expand.grid to create a matrix containing all possible > pairs of Keys (unique identifiers) from Group 1 and Group 2 and a > placeholder for each pairwise distance in an effort to pre-allocate > memory. > > The data containing the covariates are currently in a matrix that > looks like: > > x1 x2 x3 ... xn Key Group > > where x1,...,xn are the covariates of interest. The Key values > correspond to the row number. > > I'm trying to figure out a way to calculate all of the distances by > vectorizing a loop. I'm trying to avoid the nested-loop paradigm. I'm > sure I'm missing something quite obvious. > > Any insights would be appreciated. > > Best, > > Tim > > ______________________________________________ > [EMAIL PROTECTED] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html Petr Pikal [EMAIL PROTECTED] ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html