Re: [Matplotlib-users] modifying colorbar ticklabels

[Eric F. <ef...@ha...>]

Jae-Joon Lee wrote:
> On Wed, Jan 20, 2010 at 2:04 PM, Eric Firing <ef...@ha...> wrote:
>> The reason for this fudge in contour is that contourf fills
>> lower < z <= upper
>> for each consecutive pair of contour levels.
>> When the minimum value of z coincides with the lowest level, then regions
>> with that minimum are left blank; so the lowest level is adjusted downward
>> slightly, making the lowest contour interval include the minimum value.
>>
> 
> I understand levels can be adjusted for a better contouring, but I'm
> not sure whether this change needs to be visible to users.
> 
> The autoleveler, initially creates following levels
> 
> [0, 1.5, 3, 4.5, 6, 7.5, 9.]
> 
> But due to the reason you described above, they become
> 
> array([ -9.00000000e-06,   1.50000000e+00,   3.00000000e+00,
>          4.50000000e+00,   6.00000000e+00,   7.50000000e+00,
>          9.00000900e+00])
> 
> And the colorbar uses the adjusted levels for labeling. But I think it
> may make more sense to use the initial levels (at least for the
> colorbar ticks).

JJ,

I changed my mind and decided you are correct in thinking the change 
should be made in contour.py.  I now make the bottom boundary adjustment 
at the last possible time, and in such a way that it does not change the 
  levels array at all.  Therefore the colorbar never sees it, and the 
result of explicitly supplying a set of levels is identical to the case 
where those levels result from autoscaling.

Eric
> 
> Regards,
> 
> -JJ