Darren Dale wrote:
> A while back, I put some effort into rendering an offset ticklabel, which
> allowed the user to do something like
>
> plot(linspace(100000100, 100000200, 100))
>
> and the plot would look like a plot from 0 to 100, with a "+100000100"
> rendered in a new label near the far end of the axis. This doesnt work quite
> as well as it used to, because the axes autoscaling is setting the plot range
> to something like the average plus and minus 6%. I have tried tracing the
> source of this change, but I can't find it. It might be buried in the
> _transforms extension code, and I've never been able to wrap my head around
> mpl's transforms.
>
> Does anyone know why autoscaling is defaulting to this +-6% range? Does it
> have to be this way? I'm trying to improve the scalar formatter (supporting
> engineering notation, cleaning up the code).
Yes. It is not a +-6% range in general, rather it is an adjustment that
is made if the range is very small. The relevant method in Locator is:
def nonsingular(self, vmin, vmax, expander=0.001, tiny=1e-6):
if vmax < vmin:
vmin, vmax = vmax, vmin
if vmax - vmin <= max(abs(vmin), abs(vmax)) * tiny:
if vmin==0.0:
vmin -= 1
vmax += 1
else:
vmin -= expander*abs(vmin)
vmax += expander*abs(vmax)
return vmin, vmax
I know I did it this way for a reason, but I don't remember exactly what
it was--whether it was because of problems with zooming when the zoom
range gets too small (this was definitely a big problem), or because of
problems with the rest of the locator code, or because it seemed to me
to be roughly the desired behavior in most cases. Maybe it was all of
the above. Certainly, something like this is needed--I think you will
find that things go bad rapidly if vmin gets too close to vmax. I put
in the "expander" and "tiny" kwargs in case of future need, but only
expander is non-default (e.g., 0.05) in other parts of ticker.py, and
neither kwarg is presently exposed to the user. That could be changed.
Eric
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