Scatterplots
It can be used to project high-dimensional data to 2-dimensions.
In this approach, an N*N grid of parallel projections of
the data are generated. Each of these is a simple xy plot
for the two dimensions it represents. The horizontal
dimension of a scatterplot is controlled by the column it
resides in, and likewise the vertical dimension is controlled
by the row. At the top of each column and at the left
of each row is a label that shows what dimensions that
row/column represents.
This technique can be used to find the linear features, which
indicate a pairwise relationship within the data.