Re: [Matplotlib-users] xzeroaxis

[Andrew S. <str...@as...>]

John Hunter wrote:

>>>>>>"Alan" == Alan G Isaac <ai...@am...> writes:
>>>>>>            
>>>>>>
>
>    Alan> Now that you have given us axhline as a generalization of
>    Alan> gnuplot's set xzeroaxis please consider letting xticks take
>    Alan> an optional "loc" argument, which could either be "border"
>    Alan> or a number to be interpreted as a 'y' value.
>
>    Alan> So, e.g., axhline() xticks(arange(5),loc=0) would draw an
>    Alan> xzeroaxis and put the xtics along it.
>
>  
>
I tried your suggestion in gnuplot, and I found the results to be ugly 
-- the ticks straddled the axis line, rather than being inside or 
outside.  But I see, in theory, what you mean.

>However, there is a rub.  Sometimes you probably want to place the
>xaxes y location in data units, eg at y=0.  Note that this is not the
>same as y=0 in axes coords, which is always the bottom of the
>rectangle.  This is possible since matplotlib lets you specify the x
>and y data in different data coordinate systems, eg with
>http://matplotlib.sourceforge.net/matplotlib.transforms.html#-blend_xy_sep_transform,
>  
>
Hmm... that URL is not working for me, but I found what you referenced 
at http://matplotlib.sourceforge.net/matplotlib.transforms.html

>but I think it would take some work to make the interface easy and
>intuitive.  The other trick, from the developer side, is to couple the
>location of the ticks and tick labels to the y coord of the axes line.
>Doable, certainly, but would require some redesign because currently
>they all "know" their location.
>  
>
It seems using scipy's traits object for its ability to set observers on 
a variable may be useful here.

As I said earlier, I may take a stab at this, but I always feel as if 
I'm "hacking in the dark" when I try and grasp matplotlib's transform 
and render model...  When/if I look at this in greater detail, I'll 
surely let you know! :)

If you're going to a new render model in the future (kiva?), I wonder 
how useful or long-term would any changes I made now be?

Cheers!
Andrew