They&#x27;re just trying to illustrate 7 dimensional data. There are 6<i>7 2-dimensional comparisons, scatterplots, 6</i>7&#x2F;2 if you eliminate ones made redundant by symmetry, 6*7&#x2F;2+7 if you add 1-dimensional histograms for &quot;self comparisons&quot;.<p>So a scatterplot matrix, a splom, displays those 21 scatterplots in a meaningful way. Each &quot;row&quot; and &quot;column&quot; of scatterplots compares a single dimension against all of the others.<p>You usually look at a thing like this to see if you&#x27;ll get lucky and find a good &quot;orthogonal&quot; comparator—in other words, that just two normal, human-interpretable dimensions already form a good splitting plane like &quot;elevation cross $&#x2F;sq-ft&quot; does in the running example.