Re: [Matplotlib-users] pick markers only but not the connecting line

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

On 2014/06/07, 5:03 PM, C M wrote:
>
>
>
> On Sat, Jun 7, 2014 at 10:18 PM, Eric Firing <ef...@ha...
> <mailto:ef...@ha...>> wrote:
>
>     On 2014/06/07, 4:12 PM, C M wrote:
>      > I had been using a custom function (written originally by
>     Jae-Joon and
>      > modified a little by me...quite a long time back now) that was
>     working
>      > to allow point picking of markers, but *not* the line connecting
>     them.
>      > However, I've now discovered with the help of this list that the
>      > function I am using has the disadvantage that if there are more
>     than 100
>      > data points, I can't get the correct index for the picked marker
>     (turned
>      > out not to be a mpl bug:
>      > https://github.com/matplotlib/matplotlib/issues/3124).
>      >
>      > So I can just use the default pick event, but then the user can pick
>      > anywhere on the connecting line, which is meaningless in this
>     use--so I
>      > don't want them to be able to pick on the connecting line.
>
>     Why not just execute plot twice, once with the markers, with picking
>     activated, and a second time with the line, with picking inactive (the
>     default).
>
>     Eric
>
>
> That is so simple, and I hadn't thought of it at all.  Thank you!  My
> only concerns would be for slowness of plotting if there are a lot of
> points and just code simplicity, and so if there could be some other way
> with a custom function for the picker that would do this, I would
> probably prefer that. But maybe neither of these are particularly
> important concerns.

I think you will find plotting two lines instead of one is not at all 
prohibitive with respect to speed; especially when you are zooming, so 
that the number of points being plotted is not so large.

As for simplicity, two calls to a standard function with almost the same 
arguments beats an arcane special-purpose function!

If you want to make your own picker, though, it looks like you could use 
a slight modification of Line2D.contains(); it would be just a matter of 
copying it and replacing this section

             # Check for collision
             if self._linestyle in ['None', None]:
                 # If no line, return the nearby point(s)
                 d = (xt - mouseevent.x) ** 2 + (yt - mouseevent.y) ** 2
                 ind, = np.nonzero(np.less_equal(d, pixels ** 2))
             else:
                 # If line, return the nearby segment(s)
                 ind = segment_hits(mouseevent.x, mouseevent.y, xt, yt, 
pixels)


with the code in the first option--that is, without checking the 
_linestyle.  You would also need to remove the first two lines after the 
docstring.

Eric

>
> Che
>
>
>
>
>
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