Added feature for specifying uniform handle sizes for scatter plost. #4257

leeonadoh · 2015-03-21T21:27:53Z

Fix for issue #3225
The user can choose to provide the scatter_uni_size keyword within the call to pyplot.legend, which will set the legend handles to be of the specified size:

x1, y1 = [1, 1]
x2, y2 = [1, 2]
plt.figure()
plt.scatter(x1, y1, marker='o', label='first', s=20, c='b')
plt.scatter(x2, y2, marker='o', label='second', s=50, c='r')
plt.legend(scatter_uni_size=30)
# plt.legend(handler_map={PathCollection: lh.HandlerPathCollection()}, scatter_uni_size=30)
plt.show()

Switching plt.legend(scatter_uni_size=30) with the commented line, we see that a warning is thrown if the user provides their own custom handler, while specifying scatter_uni_size. In this case, scatter_uni_size is ignored.

In contrast with #4247, this fix works by defining a custom handler for PathCollection that sets the size to the one given. This fix does not modify the default mappings, as it can modify more than just the intended subplot, demonstrated by the following:

x1, y1 = [1, 1]
x2, y2 = [1, 2]
x3, y3 = [1, 1]
x4, y4 = [1, 2]

plt.figure(1)
plt.subplot(211)
plt.scatter(x1, y1, marker='o', label='first', s=20, c='b')
plt.scatter(x2, y2, marker='o', label='second', s=50., c='r')
legend.Legend.update_default_handler_map({
    PathCollection: lh.HandlerPathCollection(sizes=[30])})
plt.legend()

# Modifying the default handler mapping propagates the changes to the below as well.
plt.subplot(212)
plt.scatter(x3, y3, marker='o', label='third', s=20, c='b')
plt.scatter(x4, y4, marker='o', label='fourth', s=50, c='r')
plt.legend()
plt.show()

The 2nd subplot will also recieve the changes done to the default mapping. However, by replacing

legend.Legend.update_default_handler_map({
    PathCollection: lh.HandlerPathCollection(sizes=[30])})
plt.legend()

with

plt.legend(scatter_uni_size=30)

the 2nd subplot will remain unaffected.

Tests will be implemented soon.

tacaswell · 2015-03-30T03:37:45Z

lib/matplotlib/legend.py

+            if (self._custom_handler_map is not None and
+                    PathCollection in self._custom_handler_map):
+                warnings.warn("'scatter_uni_size' was set, but custom " +
+                              "handler was provided. The former will " +


Please be explicit, I would say "'scatter_uni_size will be ignored'". (This is mostly because I personally always have to stop and think about which one is 'former' and which one is 'later').

I this might be a reasonable place to raise an Exception as the user has passed in conflicting inputs. Not 100% sold on that though.

tacaswell · 2015-03-30T03:42:41Z

👍 modulo comment warning.

attn @pelson Any comments on the changes to

Could you please add an entry to https://github.com/matplotlib/matplotlib/tree/master/doc/users/whats_new ?

tacaswell · 2015-04-12T00:13:17Z

@leeonadoh @ryanbelt Can you add an entry in whats_new? This helps to make sure that your new feature is discover-able and highlighted when we release the next feature version.

leeonadoh · 2015-04-12T00:37:18Z

Sorry for not giving an update. There's currently a better solution in the works, which will generalize this feature to all types of plots. We'll add the whats_new entry when we have that ready.

tacaswell · 2015-04-12T01:03:54Z

Ah, great to hear!

Please feel free to share early and often to get feed back.

TODO: Modify axes.legend and axes.figlegend to use UniformLegend when uniform size is desired.

leeonadoh · 2015-04-18T05:07:47Z

The updated solution is able to give all types of plots a uniform size when displayed on the legend.

It works by creating a subclass of Legend called UniformLegend that specifies its own list of default handlers. These default handlers will ensure an uniform size.

Currently, the code to use UniformLegend has not been written. The idea however, is similar to the old solution where we introduce a new parameter set_uni_size to axes.legend() and axes.figlegend(). When set_uni_size is specified, we check to ensure that no conflicting parameters are specified (custom handlers, marker scale, etc), and return an instance of UniformLegend instead of just Legend.

tacaswell · 2015-04-18T05:38:59Z

lib/matplotlib/legend.py

@@ -803,7 +803,7 @@ def get_title(self):
        return self._legend_title_box._text

    def get_window_extent(self, *args, **kwargs):
-        'return a extent of the legend'
+        'return a extent of the the legend'


typo (that was fixed and this adds back in?)

Oops! Missed that when merging. Fixed in 3f0ae27

Modified `Axes.legend` and `Figure.legend` to support `uniform_size`. Added checks to throw exception on conflicting parameters. `uniform_size` specified with `markerscale` or `handler_map`.

leeonadoh · 2015-04-18T20:47:50Z

TODO: Unit tests.
Would image testing be required for this? I think checking the marker size would suffice.

jenshnielsen · 2015-04-19T10:12:11Z

If possible I would generally prefer tests checking marker sizes over image comparison tests.

pelson · 2015-04-21T06:42:20Z

This seems like a lot of work for this feature, and I wonder if there is a neater approach. It seems that the key part of this is to set_markersize on each of the handlers of interest.

Rather than implementing a very specific keyword, I'd be looking at simplifying the ability to change the legend class which is used from plt.legend()/ax.legend() at https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/axes/_axes.py#L509.

With the ability to switch the legend class, I'd then be looking for the best place to override so that I can get the behaviour I wanted. It isn't entirely clear where the handler responsibility lies within the Legend class, but I'd probably plump for Legend._init_legend_box purely for the fact that the handles are created in there https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/legend.py#L717

It is worth noting, that there is a bit of a smell in the legend code at the moment - some of the artists from the handles are not referenced within legend itself, as there appears to have been an assumption of 1-to-1 mapping of handler to artists. https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/legend_handler.py#L205-L208

So with all of this, I'd be looking at (untested):

from matplotlib.legend import Legend
from matplotlib.legend_handler as legend_handler

uniform_size_cases = {legend_handler.HandlerLine2D: lambda handler: 

class UniformSizeLegend(Legend):
    def __init__(self, *args, **kwargs):
        super(UniformSizeLegend, self).__init__(*args, **kwargs)
        self.uniform_size = kwargs.get('uniform_size', 30)

    def _init_legend_box(self, *args, **kwargs):
        super(UniformSizeLegend, self)._init_legend_box(*args, **kwargs)
        for artist in self.legendHandles:
            if hasattr(artist, '_legmarker'):
                artist._legmarker.set_markersize(self.uniform_size)
            elif hasattr(artist, 'set_markersize'):
                artist.set_markersize(self.uniform_size)

And I'd call it with:

plt.legend(uniform_size=20, legend_class=UniformSizeLegend)

Just an alternative thought to the problem.

HTH

tacaswell · 2015-06-17T04:15:07Z

Moved to 'proprosed next point release' meaning this is not a blocker for the next release, but can go in if it is ready.

This needs a re-base and @pelson 's comments on a possible re-think have not been addressed.

jklymak · 2018-10-06T00:45:54Z

Closing as abandoned. Seems like it is also in #11127

ImportanceOfBeingErnest · 2018-10-06T01:34:28Z

#11127 is a bit different, it would create many legend entries for a single scatterplot. The idea here was to unify the size of different scatter plot's handles. Many options are shown in the stackoverflow question "setting a fixed size for points in legend". The easiest is just:

legend = plt.legend()
for legobj in legend.legendHandles:
    legobj.set_sizes([64])

My faviourite, which I just added to that thread as well would be to use the update function of the Handler.

def update(handle, orig):
    handle.update_from(orig)
    handle.set_sizes([64])

plt.legend(handler_map={PathCollection : HandlerPathCollection(update_func=update)})

tacaswell added the status: needs review label Mar 21, 2015

tacaswell added this to the next point release milestone Mar 22, 2015

rrrkren mentioned this pull request Mar 26, 2015

Implemented Issue #3225. Added a uniform_size parameter to legend. #4247

Closed

tacaswell reviewed Mar 30, 2015
View reviewed changes

leeonadoh force-pushed the master branch from b007db7 to 45e1290 Compare April 10, 2015 17:55

tacaswell added status: needs revision and removed status: needs review labels Apr 12, 2015

Introduced UniformLegend class and associated handlers.

9cb6472

TODO: Modify axes.legend and axes.figlegend to use UniformLegend when uniform size is desired.

leeonadoh force-pushed the master branch from 45e1290 to 9cb6472 Compare April 18, 2015 05:01

tacaswell reviewed Apr 18, 2015
View reviewed changes

leeonadoh added 2 commits April 18, 2015 14:40

fixing for pep8

3f0ae27

Added support for uniform_size

455f580

Modified `Axes.legend` and `Figure.legend` to support `uniform_size`. Added checks to throw exception on conflicting parameters. `uniform_size` specified with `markerscale` or `handler_map`.

tacaswell modified the milestones: proposed next point release, next point release Jun 17, 2015

petehuang mentioned this pull request Dec 29, 2016

Setting a fixed size for points in legend #3225

Closed

tacaswell modified the milestone: 2.1 (next point release) Aug 29, 2017

jklymak closed this Oct 6, 2018

jklymak mentioned this pull request Oct 6, 2018

Change the size of legend markers... #12417

Open

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Added feature for specifying uniform handle sizes for scatter plost. #4257

Added feature for specifying uniform handle sizes for scatter plost. #4257

leeonadoh commented Mar 21, 2015

tacaswell Mar 30, 2015

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tacaswell Apr 18, 2015

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jenshnielsen commented Apr 19, 2015

pelson commented Apr 21, 2015

tacaswell commented Jun 17, 2015

jklymak commented Oct 6, 2018

ImportanceOfBeingErnest commented Oct 6, 2018

Added feature for specifying uniform handle sizes for scatter plost. #4257

Added feature for specifying uniform handle sizes for scatter plost. #4257

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