Scatterplot matrices are one of the most practical direct visualization of unstructured data sets—provided that the dimensionality does not become too large. Despite their prominence in the visualization community, there are few non-commercial tools out there that are able to produce scatterplot matrices for publication-ready visualizations.

In this post, I want to briefly explain how to use a recent version of gnuplot, one of my favourite plotting tools, to create something that resembles a scatterplot matrix. In this example, I will use “the famous Iris data set”, which I am sure everyone is familiar with by now.