There are a few different plot functions for CGGP objects:
`CGGPplotblocks`, `CGGPplotblockselection`,
`CGGPplotcorr`, `CGGPplotheat`, `CGGPplothist`,
`CGGPvalplot`,
`CGGPplotslice`, `CGGPplotslice`, and `CGGPplotvariogram`.
Currently `CGGPplotblocks` is the default plot object.