[R] Convert back to lower triangular matrix
David Winsemius
dwinsemius at comcast.net
Tue Nov 15 23:57:17 CET 2011
On Nov 15, 2011, at 5:38 PM, Juliet Ndukum wrote:
> Given a vector;> ab = seq(0.5,1, by=0.1)
> > ab[1] 0.5 0.6 0.7 0.8 0.9 1.0
> The euclidean distance between the vector elements is given by the
> lower triangular matrix
> > dd1 = dist(ab,"euclidean")
> > dd1 1 2 3 4 5
> 2 0.1
> 3 0.2 0.1
> 4 0.3 0.2 0.1
> 5 0.4 0.3 0.2 0.1
> 6 0.5 0.4 0.3 0.2 0.1
> Convert the lower triangular matrix to a full matrix
> > ddm = as.matrix(dd1)
> > ddm 1 2 3 4 5 61 0.0 0.1 0.2 0.3 0.4 0.52 0.1 0.0 0.1
> 0.2 0.3 0.43 0.2 0.1 0.0 0.1 0.2 0.34 0.3 0.2 0.1 0.0 0.1 0.25 0.4
> 0.3 0.2 0.1 0.0 0.16 0.5 0.4 0.3 0.2 0.1 0.0
> I would be grateful if someone could provide me with a code to
> convert ddm to the lower triangular matrix as before i.e. dd1
Surely this would be the logical inverse
dd1.b <- as.dist(ddm)
--
David Winsemius, MD
West Hartford, CT
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