Phylogenetically Independent Contrasts
Compute the phylogenetically independent contrasts using the method described by Felsenstein (1985).
pic(x, phy, scaled = TRUE, var.contrasts = FALSE)
x has names, its values are matched to the tip labels of
phy, otherwise its values are taken to be in the same order
than the tip labels of
The user must be careful here since the function requires that both
series of names perfectly match, so this operation may fail if there
is a typing or syntax error. If both series of names do not match, the
values in the
x are taken to be in the same order than the tip
phy, and a warning message is issued.
either a vector of phylogenetically independent contrasts (if
var.contrasts = FALSE), or a two-column matrix with the
phylogenetically independent contrasts in the first column and their
expected variance in the second column (if
TRUE). If the tree has node labels, these are used as labels of the
Felsenstein, J. (1985) Phylogenies and the comparative method. American Naturalist, 125, 1--15.
### The example in Phylip 3.5c (originally from Lynch 1991) cat("((((Homo:0.21,Pongo:0.21):0.28,", "Macaca:0.49):0.13,Ateles:0.62):0.38,Galago:1.00);", file = "ex.tre", sep = "") tree.primates <- read.tree("ex.tre") X <- c(4.09434, 3.61092, 2.37024, 2.02815, -1.46968) Y <- c(4.74493, 3.33220, 3.36730, 2.89037, 2.30259) names(X) <- names(Y) <- c("Homo", "Pongo", "Macaca", "Ateles", "Galago") pic.X <- pic(X, tree.primates) pic.Y <- pic(Y, tree.primates) cor.test(pic.X, pic.Y) lm(pic.Y ~ pic.X - 1) # both regressions lm(pic.X ~ pic.Y - 1) # through the origin unlink("ex.tre") # delete the file "ex.tre"