def create_gamma_model(alignment, missing_data=None, ncat=4):
""" Create a phylo_utils.likelihood.GammaMixture for calculating
likelihood on a tree, from a treeCl.Alignment and its matching
treeCl.Parameters """
model = alignment.parameters.partitions.model
freqs = alignment.parameters.partitions.frequencies
alpha = alignment.parameters.partitions.alpha
if model == 'LG':
subs_model = LG(freqs)
elif model == 'WAG':
subs_model = WAG(freqs)
elif model == 'GTR':
rates = alignment.parameters.partitions.rates
subs_model = GTR(rates, freqs, True)
else:
raise ValueError("Can't handle this model: {}".format(model))
tm = TransitionMatrix(subs_model)
gamma = GammaMixture(alpha, ncat)
gamma.init_models(tm, alignment_to_partials(alignment, missing_data))
return gamma
