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Scatterplot matrices (pair plots) with cdata and ggplot2

In my previous post, I showed how to use cdata package along with ggplot2‘s faceting facility to compactly plot two related graphs from the same data. This got me thinking: can I use cdata to produce a ggplot2 version of a scatterplot matrix, or pairs plot?

A pairs plot compactly plots every (numeric) variable in a dataset against every other one. In base plot, you would use the pairs() function. Here is the base version of the pairs plot of the iris dataset:

pairs(iris[1:4], 
      main = "Anderson's Iris Data -- 3 species",
      pch = 21, 
      bg = c("#1b9e77", "#d95f02", "#7570b3")[unclass(iris$Species)])

Unnamed chunk 1 1

There are other ways to do this, too:

# not run

library(ggplot2)
library(GGally)
ggpairs(iris, columns=1:4, aes(color=Species)) + 
  ggtitle("Anderson's Iris Data -- 3 species")

library(lattice)
splom(iris[1:4], 
      groups=iris$Species, 
      main="Anderson's Iris Data -- 3 species")

But I wanted to see if cdata was up to the task. So here we go….

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