I’m playing with heat/contour maps and seeing some strange behavior:
AFAIK contour lines should never cross in the way they do in the lower left.
JFYI, this data is basically a CDF of a 2-dimensional distribution (i.e. dz/dx and dz/dy are always <= 0); which means there shouldn’t be any complicated shapes (e.g. “islands”) in the contours, and indeed plot.ly seems to get them mostly correct, so the intersections might just be artifacts from whatever (quadratic bezier?) smoothing is happening.
lmk if more info would be useful or if there’s a better place to post apparent issues like this.