messy visualization or crash for degenerate input

[mlesnick]

Corner cases with at most a single x-grade or y-grade are not handled properly in the visualizer. This is true in particular for the empty bifiltration. [EDIT: Some of this has been addressed, see the comment below.]

For example, see the following (note that the axis label sits on top of the bounds for the axis):

I suppose this is just a matter of changing the width of the displayed regions in the corner cases.

Also, in the case of the empty bifiltration, resizing the window immediately crashes the visualizer (OS X Sierra).

[mlesnick]

The visualization also has problems with very nearly degenerate data. In the attached example,

I put a gaussian kernel density estimator on a circle with 15 equally spaced points. The codensity values are identical, up to a VERY SMALL but nonzero numerical error.

For H0 and 30x30 bins, the visualizer gives this:

CameronTest5.txt

[mlesnick]

Simon did some changes, now in a pull request, that addresses most of this. The corner case of empty input is still not addressed. And the degenerate case of "camerontest5" is still not handled correctly; now the slice line never shows.