Phylogenetically Independent Contrasts
Compute the phylogenetically independent contrasts using the method described by Felsenstein (1985).
pic(x, phy, scaled = TRUE, var.contrasts = FALSE)
- a numeric vector.
- an object of class
- logical, indicates whether the contrasts should be
scaled with their expected variance (default to
- logical, indicates whether the expected
variance of the contrasts should be returned (default to
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
var.contrasts = TRUE).
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"