gbm.R

library(jpeg)
library(plyr)

# Read in Girl before a Mirror from somewhere

# readJPEG only accepts a path, so give it one without much tomfoolery
picasso.path <- tempfile('girl_before_a_mirror.jpg')
download.file('http://bobholt.me/images/girl_before_a_mirror.jpg', picasso.path)

gbm <- readJPEG(picasso.path)
unlink(picasso.path)

# helper function to plot eigenvalues
plotEigen <- function(m) {
  # Gimme a square matrix
  corMat <- cor(t(m))
  y <- eigen(corMat)$values
  plot(y = y, x = seq_along(y), log = "x", las = 1)
}

# cheap way to get multiple plots on a single page
old.par <- par(mfrow = c(1,1))
LO <- layout(matrix(1:6, ncol=2))

# Each channel is a m * n matrix
# we use a_ply because plot is called for side effects and we don't need a return value
a_ply(gbm, 3, plotEigen)
# prcomp has a plot method. Yay.
a_ply(gbm, 3, function(x) {plot(prcomp(x))})

par(old.par)