The same clipping problem someone stated before applies also to StepPlots. If one point is on the left but outside the screen area and the other on the right but out side the screen area, the chart is not drawn.
I would suggest to change the clipping algorithm in StepPlots.cs to something like:
// do horizontal clipping here, to speed up
if ((p1.X < leftCutoff && p2.X < leftCutoff && p3.X...
2009-04-06 14:08:51 UTC in NPlot Charting Library
