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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Better deal with Numpy array subclasses in methods other than plot and scatter","articleBody":"The `plot` and `scatter` methods now deal nicely with Numpy array sub-classes, such as Astropy quantities (which have attached units):\n\n``` python\nIn [1]: from astropy import units as u\n\nIn [2]: import matplotlib.pyplot as plt\n\nIn [3]: fig = plt.figure()\n\nIn [4]: ax = fig.add_subplot(1,1,1)\n\nIn [5]: x = [1,2] * u.m\n\nIn [6]: y = [3,4] * u.m\n\nIn [7]: ax.plot(x,y)\nOut[7]: [\u003cmatplotlib.lines.Line2D at 0x107f00048\u003e]\n\nIn [8]: ax.scatter(x, y)\nOut[8]: \u003cmatplotlib.collections.PathCollection at 0x107f00ba8\u003e\n```\n\nHowever, other methods such as `axhline` and `axvline` do not:\n\n``` python\nIn [9]: z = 4 * u.m\n\nIn [10]: ax.axhline(z)\n---------------------------------------------------------------------------\nUnitsError                                Traceback (most recent call last)\n\u003cipython-input-10-39d10b51e434\u003e in \u003cmodule\u003e()\n----\u003e 1 ax.axhline(z)\n\n/Users/tom/miniconda3/envs/production35/lib/python3.5/site-packages/matplotlib/axes/_axes.py in axhline(self, y, xmin, xmax, **kwargs)\n    744         self._process_unit_info(ydata=y, kwargs=kwargs)\n    745         yy = self.convert_yunits(y)\n--\u003e 746         scaley = (yy \u003c ymin) or (yy \u003e ymax)\n    747 \n    748         trans = self.get_yaxis_transform(which='grid')\n\n/Users/tom/miniconda3/envs/production35/lib/python3.5/site-packages/astropy/units/quantity.py in __array_prepare__(self, obj, context)\n    344                                      \"argument is not a quantity (unless the \"\n    345                                      \"latter is all zero/infinity/nan)\"\n--\u003e 346                                      .format(function.__name__))\n    347             except TypeError:\n    348                 # _can_have_arbitrary_unit failed: arg could not be compared\n\nUnitsError: Can only apply 'less' function to dimensionless quantities when other argument is not a quantity (unless the latter is all zero/infinity/nan)\n```\n\nIt would be nice to try and make these methods also support Numpy array sub-classes.\n","author":{"url":"https://github.com/astrofrog","@type":"Person","name":"astrofrog"},"datePublished":"2016-01-21T22:55:06.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":10},"url":"https://github.com/5896/matplotlib/issues/5896"}