This function attempts to ask if the rate of a continuous character, y, depends on the state of a separate continuous trait, x. This is accomplished by regressing the squared contrasts in y on the branch or node ancestral estimates of x.
ratebystate(tree, x, y, nsim=100, corr=c("pearson","spearman"), ...)phylogenetic tree.
a continuous character - the dependent variable in the model.
a second continuous trait - the response variable.
number of simulations for hypothesis testing.
correlation method to use. Same as in cor.
optional arguments which include sim.method ("fastBM" or "sim.corrs"; see fastBM and sim.corrs); method ("by.node" or "by.branch" indicating whether to assume the rate varies as a function of the node state or the mean branch state); message - a logical value indicating whether or not to return corr and method; finally logarithm - indicating whether or not to fit a model in which the variance of Brownian evolution in y changes as a multiplicative function of x. The default is logarithm=FALSE.
This function returns an object of class "ratebystate" with up to the following four elements:
value of the regression coefficient for square of the contrasts in y regressed on the ancestral or branch-wise estimated states for x.
correlation coefficient for corr=corr.
string giving the value of corr.
string giving the value of method.
Revell, L. J. (2012) phytools: An R package for phylogenetic comparative biology (and other things). Methods Ecol. Evol., 3, 217-223.