Re: [matplotlib-devel] Plots with two scales for the y axis

[Baptiste C. <bap...@al...>]

John Hunter a =E9crit :
> I have added some changes to CVS to support sharex and sharey kwargs
> (I thought this was a better name than twinx and twiny).  I had to
> make some minor changes to axis to support sharing tick locators and
> formatters, but nothing substantial.  You can now instantiate an axes
> with, eg
>=20
>   subplot(212, sharex=3Dax1)
>=20
> and ditto for sharey.  The view limits, transform function, and tick
> Locator and Formatter are shared.  This allows you to pan and zoom on
> one axes and have the others follow, which is very nice.  There is a
> new example showing how to use this example/shared_axis_demo.py.
>=20
Hi John,

I like this implementation a lot. Cool stuff !

> I was able to remove the TwinAxes class altogether and use the shared
> kwargs in its stead, which is cleaner.  I preserved the "twin"
> convenience function (naming it twinx) and all it does is pass the
> proper kwargs and make the calls to tick_right.
> examples/two_scales.py is updated
>=20
you also need to call tick_left on the original axis, but that is a=20
minor correction.

> I don't think the datalim need to be shared because they are
> responsible only for autoscaling.
>
There is still a problem because autoscaling is disabled on the second=20
axes. I have an idea on how to solve this, I'll try it and send a patch=20
later in the week.

> One possibility is to leave inaxes, xdata and ydata alone which
> satisfies both problems above.  And then to add a new attribute, axseq
> which is a list of (ax, xdata, ydata ) tuples to handle the
> overlapping axes case.  Internally, we could use axseq so that pan/zoom
> will be handled properly in the two_scales case.  The draw back here
> is that having more than one obvious way to do it may also confuse
> people down the road.
>=20
This sounds reasonable to me. I don't think it is confusing. If people=20
know what to do with multiple axes, they'll go with axseq, if not=20
inaxes, xdata and ydata will provide the most reasonable choice for them.
I'll play a little bit with this, and see if it breaks anything I use.

Cheers,
BC