Re: [Matplotlib-users] Bug with setting axis limits

[John H. <jdh...@ac...>]

>>>>> "Srinath" == Srinath Avadhanula <sr...@fa...> writes:

    Srinath> Hello, I seem to have uncovered a bug in setting/updating
    Srinath> the axis limits.

Hi, I have looked into this and it is indeed a bug.  Here is what is
going on:  The transforms for x and y take your view limits and map
them to display coords, where negative numbers don't make sense.  It
is a standard linear transformation

        scale = displayInterval/viewInterval
        return  scale*(y-viewMin) + displayMin

In your example, if the y axis view limits are [0.516, 0.52] and the
display interval is [44.0, 360.0], then transformation of the y vector
[0, 1].

  scale = (360-44)/0.004
  ytransformed = scale*(y-.516) + 44

which is  [-40720., 38280.]

Ie, when your nearest data point is much smaller than your view
limits, you get negative display coords which are undefined.  I am not
sure this case is common enough to warrant the performance hit of
detecting it and doing the linear interpolation necessary to add
pseudo data points to make your plot well defined.  Simply replacing
the negative data with 0 is incorrect because you have to do linear
interpolation to get the right location in display coords.  Perhaps a
warning if min(xtransformed)<0 or min(ytransformed)<0 would be
appropriate and worth the performance hit.

If you have some ideas on what is the best way to handle this case,
let me know.

JDH