[R] replacing elements of distance matrix

[Nikhil Kaza]

replace dist with mahalanobis distance in the following example.

a <- cbind(runif(10), sample(1:3, 10, replace=T))
a.L <- split(a,a[,2])
dist.L <- lapply(a.L, dist)



Nikhil Kaza
Asst. Professor,
City and Regional Planning
University of North Carolina

nikhil.list at gmail.com

On Jul 19, 2010, at 9:24 AM, Michael Ralph M. Abrigo wrote:

> Hi! I am trying to implement non-bipartite matching. I have around  
> 500 sites
> which can be clustered by 10 regions. I am able to calculate pairwise
> Mahalanobis distances between sites (thanks to another post in the  
> forum).
> However, I want to constrain my match to sites within the same  
> region. Thus
> I want to replace elements of the distance matrix with a high value,  
> say
> 999999, for sites not of the same region so that the pair will not be
> matched.
> In the original data file I have information on which sites belong  
> to what
> region. However, when I compute for pairwise Mahalanobis distances,  
> I only
> use a subset of the file, which, naturally, does not include the
> georeference of the sites. How should I do this? Any hint will be most
> appreciated.
> Btw, I am relatively new in using R. I may export the matrix to  
> another
> program and replace the elements there, but that is a very very  
> dirty and
> rough trick that I would rather not do given better options.
> Many thanks in advance.
>
> Cheers,
> Michael
>
> -- 
> "I am most anxious for liberties for our country... but I place as a  
> prior
> condition the education of the people so that our country may have an
> individuality of its own and make itself worthy of liberties... " Jose
> Rizal,1896
>
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