Rodrigo Aluizio wrote:
Hi again List,
Well this time I?m writing for a friend (really J). He needs to create a
distance matrix based on an abundance matrix using the 1-Pearson?s R index.
Well I told him to look at the proxy package, but there is only Pearson
Index. He needs it to perform a clustering. Well, as soon as he told me
there proxy only had the Pearson index I thought: ?He could just do
something like
NewObject<-1-PearsonMatrixObject?
But I didn?t tell him that because I?m not sure it?s the same thing, and it
probably will generate a strange cluster with the braches ends distant from
the base?
He told me that Statistica 7.0 has this Index, but he doesn?t own it. So? Is
there a way on R to do this correctly?
Thanks for the attention.
The help file of dist has an example how to do this:
>?dist
## Use correlations between variables "as distance"
dd <- as.dist((1 - cor(USJudgeRatings))/2)
Note the division by 2! Correlations can be between -1 ... +1 and
negative distances make no sense.
Another approach is r^2, but this has, of course, a different
interpretation.
ThPe
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