These functions calculate weight matrices from regimes specified by a bayou formatted parameter list
parmap.W calculates the weight matrix for a set of regimes from a phylogeny
with a stored regime history. .parmap.W calculates the same matrix, but without checks and is
generally run internally.
parmap.W(tree, pars)either a tree of class "phylo" or a cache object produced by bayOU's internal functions. Must include list element 'maps' which is a simmap reconstruction of regime history.
a list of the parameters used to calculate the weight matrix. Only pars$alpha is necessary to calculate the matrix, but others can be present.
.parmap.W is more computationally efficient within a mcmc and is used internally.