Scatterplot Matrix

[Mattriks]

The new function scatterplotmatdata produces 4 dataframes which can be used to build a scatterplot matrix via Geom.subplot_grid. I have put an example in #286. This way of producing a scatterplot matrix is very flexible, because the user can change many things in the plot, using normal Gadfly commands.

To make this work, I also fixed an error in Geom.subplot grid, so now it behaves properly when both free_x_axis and free_y_axis are true.

[versipellis]

What ever happened with this?

[Mattriks]

The branch went stale because historically Gadfly wasn't being maintained at that time. Today I'd rewrite this as a new Statistic Stat.scatterplotmatrix, which would work with Geom.subplot_grid.