Trouble with contour plot

Eric Firing <efiring-MsMAYOsy5kY3uPMLIKxrzw@...1455...> writes:

I don't know if there are any strict requirement on monotonicity for X
and Y, or if there are any cases where the plot is still valid even if
that property is violated. If it is a requirement, then I agree that
there should be a check.

For sensible output, it is a requirement. Contour and contourf (like
imshow, pcolor, and pcolormesh) work with gridded data. Gridding is the
responsibility of the user. It can be done in many different ways, so
it makes sense to keep the gridding separate from the display of the
gridded data.

If there is a check--and I am not convinced there should be--it should
provide only a warning. It is perfectly reasonable for a person to take
a dataset and contour it even if the grid is not monotonic. Sometimes
one wants to get a quick look at raw input, complete with errors.

I don't quite understand your last point. In my example, the
single jump from pi to -pi makes half of the plot constant while in
truth it is oscillatory. I would not say that this reflects the "raw
input" in any way, and I am not sure what one could learn from this plot
with a quick (or even prolonged) look.

Am I missing something? Is there some obvious connection between the
jump in Theta, the data, and the resulting plot? To me the plot looks
like unpredictable garbage, so I really don't understand how anyone
could want to do something like that...




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