Facetting in ggplot2

Question

I have this dataset: https://dl.dropboxusercontent.com/u/73950/data.csv The dataset contains 3 variables.

Here's how I visualize the data right now:

library(ggplot2)
library(reshape2)
library(RColorBrewer)

dat = read.csv("data.csv", header = FALSE)

myPalette <- colorRampPalette(rev(brewer.pal(11, "Spectral")))
sc <- scale_colour_gradientn(colours = myPalette(100))

ggplot(dat, aes(x=V1, y=V3, colour = V2))+ geom_point(alpha = .2,size = 3) + sc

Instead of just one figure, I'd like to facet the figure to display 3 different ways to attribute variables to each axis and color. As such:

• x = V1, y = V2, color = V3
• x = V1, y = V3, color = V2
• x = V2, y = V3, color = V1

How to do this kind of things with ggplot2's faceting?

Answer 1

You can get this by putting the data in the format ggplot likes. In this case, a column that can be used to split the data into facets (called var below). To do that, I just repeated the data three times, choosing the appropriate x and y variables for each 2-way combo, and using the variable left out of each combination as the coloring variable.

## Rearrange the data by 2-way combinations, the coloring is the remaining column
res <- do.call(rbind, combn(1:3, 2, function(ii)
    cbind(setNames(dat[,c(ii, setdiff(1:3, ii))], c("x", "y", "color")),
                   var=paste(ii, collapse=".")), simplify=F))

ggplot(res, aes(x=x, y=y, color=color))+ geom_point(alpha = .2,size = 3) + 
  facet_wrap(~ var, scales="free") + sc