Legend does not work for quiver

[astrofrog]

It seems that labels do not work for quiver plots:

In [1]: x = np.random.random(100)

In [2]: y = np.random.random(100)

In [3]: u = np.random.random(100) / 30.

In [4]: v = np.random.random(100) / 30.

In [5]: plt.quiver(x, y, u, v, label='test')
Out[5]: <matplotlib.quiver.Quiver at 0x1076d1890>

In [6]: plt.legend()
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/axes.py:4747: UserWarning: No labeled objects found. Use label='...' kwarg on individual plots.
  warnings.warn("No labeled objects found. "

Is support of this planned? If not, maybe it would make sense not to allow the label argument for quiver?

[tacaswell]

There is a QuiverKey class which looks like it is for this purpose. I suspect this is an issue with the auto-magic that walks the artists and generates the pairs in ax.legend().

[efiring]

Right. I don't see how a legend makes much sense for quiver. What characteristics would you give the arrow?

[astrofrog]

@efiring - what about just the same as for a line plot for the line part, but with an arrowhead that matches the plot?

[tacaswell]

@astrofrog See http://matplotlib.org/examples/pylab_examples/quiver_demo.html

I strongly suspect that you could pass a QuiverKey artist into the legend.

2020 Tom does not agree with 2014 Tom, see comment at #16664.

[tacaswell]

@astrofrog Does quiverkey do what you need? I am going to close this, please re-open if quiverkey is not what you need.