Dear All,
I'm using betadisper {vegan} and I'm interested not only in the dispersion
within the group but also the distances between the groups. With betadisper
I get distances to group centroids but is it possible to get distances to
other groups centroids?
It might be possible to do it by hand by the formula given in the
description of the betadisper (below) but I'm a bit confused how to treat
the imaginary part there...
z[ij]^c = sqrt(Delta^2(u[ij]^+, c[i]^+) - Delta^2(u[ij]^-, c[i]^-))
I would highly appreciate all the help I can get!
-Merja
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Multivariate dispersion & distances
2 messages · M Elo, Jari Oksanen
M Elo <merja.t.elo <at> luukku.com> writes:
Dear All,
I'm using betadisper {vegan} and I'm interested not only in the dispersion
within the group but also the distances between the groups. With betadisper
I get distances to group centroids but is it possible to get distances to
other groups centroids?
It might be possible to do it by hand by the formula given in the
description of the betadisper (below) but I'm a bit confused how to treat
the imaginary part there...
z[ij]^c = sqrt(Delta^2(u[ij]^+, c[i]^+) - Delta^2(u[ij]^-, c[i]^-))
I would highly appreciate all the help I can get!
Merja, You should do it exactly in the same way as you wrote above: subtract the squared Euclidean distances in the imaginary part from the squared Euclidean distances in the real part and take the square root. I think doing this by hand is the only way to do this directly. The scope of the method is to compare dispersions within groups. There are other tools to compare the locations of group centroids (adonis in vegan), but they won't give you distances. Cheers, Jari Oksanen