# Rev Language Reference

## mvLayeredScaleProposal - Rescales all the subtrees below some age.

Makes a subtree scale move on all subtrees below a given age in the tree. Tree topology is not altered.

### Usage

mvLayeredScaleProposal(TimeTree tree, RealPos lambda, Bool tune, RealPos weight, Probability tuneTarget)

### Arguments

 tree : TimeTree ( pass by reference) The tree on which this move operates. lambda : RealPos (pass by value) The strength of the proposal. Default : 1 tune : Bool (pass by value) Should we tune lambda during burnin? Default : TRUE weight : RealPos (pass by value) The weight how often on average this move will be used per iteration. Default : 1 tuneTarget : Probability (pass by value) The acceptance probability targeted by auto-tuning. Default : 0.44

### Details

The tree must be ultrametric. An age is randomly drawn between the root age and the age of the oldest tip. Then all subtrees below this age are scaled up or down depending on a scaler drawn from an exponential distribution.

### Example

# We are going to save the trees we simulate in the folder simulatedTrees:
dataFolder = "simulatedTrees/"
# Letâ€™s simulate a species tree with 10 taxa, 2 gene trees, 3 alleles per species:
n_species <- 10
n_genes <- 2
n_alleles <- 3
# we simulate an ultrametric species tree:
# Species names:
for (i in 1:n_species) {
species[i] <- taxon(taxonName="Species_"+i, speciesName="Species_"+i)
}
spTree ~ dnBirthDeath(lambda=0.3, mu=0.2, rootAge=10, rho=1, samplingStrategy="uniform", condition="nTaxa", taxa=species)
print(spTree)
# let's pick a constant effective population size of 50:
popSize <- 50
# let's simulate gene trees now:
# taxa names:
for (g in 1:n_genes) {
for (i in 1:n_species) {
for (j in 1:n_alleles) {
taxons[g][(i-1)*n_alleles+j] <- taxon(taxonName="Species_"+i+"_"+j, speciesName="Species_"+i)
}
}
geneTrees[g] ~ dnMultiSpeciesCoalescent(speciesTree=spTree, Ne=popSize, taxa=taxons[g])
print(geneTrees[g])
}
# We can save the species tree and the gene trees:
write(spTree, filename=dataFolder+"speciesTree")
# Saving the gene trees
for (i in 1:(n_genes)) {
write(geneTrees[i], filename=dataFolder+"geneTree_"+i+".tree")
}
# set my move index
mi = 0
move_species_subtree_scale = mvLayeredScaleProposal( speciesTree=spTree, weight=5 )
for (i in 1:n_genes) {
}
moves[++mi] = move_species_subtree_scale
# We get a handle on our model.
# We can use any node of our model as a handle, here we choose to use the topology.
mymodel = model(spTree)
# Monitors to check the progression of the program
monitors[1] = mnScreen(printgen=10, spTree)
# Here we use a plain MCMC. You could also set nruns=2 for a replicated analysis
# or use mcmcmc with heated chains.
mymcmc = mcmc(mymodel, monitors, moves, nruns=4)
mymcmc.run(generations=1000)
mymcmc.operatorSummary()