René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"twinx plot with datetime in xaxis fails in 3.1.3","articleBody":"### Bug report\r\n\r\n**Bug summary**\r\n\r\nin 3.1.3 ax.twinx() with fails to plot the second plot if using datetime values for x axis.\r\n\r\n**Code for reproduction**\r\n\r\n\r\n\r\n```python\r\n\r\nimport pandas as pd\r\nimport matplotlib.pyplot as plt\r\nimport matplotlib.dates as mdates\r\nimport numpy as np\r\n\r\ndf = pd.DataFrame(index=pd.date_range(start='2020-01-26 22:00:00+00:00', end='2020-02-03 14:00:00+00:00', freq='H'),\r\n                 data=np.random.rand(185, 5), columns = ['code_200','code_201','code_500','mean_200','mean_201'] )\r\nfig, ax = plt.subplots( figsize=(15,6))\r\n# plt.figure()\r\ndfd = df.resample('D')[['code_200','code_201','code_500']].sum().tail(10)\r\n# plt.bar(dfd)\r\nplt.bar(dfd.index, dfd.code_200, color='#008c6e', label='sum of 200s')\r\nplt.bar(dfd.index, dfd.code_201, bottom=dfd.code_200, color='k', label='sum of 201s')\r\nplt.bar(dfd.index, dfd.code_500, bottom=dfd.code_200+dfd.code_201, color='#872d32',label='sum of 500s')\r\n\r\nax.yaxis.grid('both',color='k', linestyle='-', alpha=0.2)\r\nax.set_ylabel('# responses')\r\ndfm = df.resample('D')[['mean_200', 'mean_201']].mean().tail(10)\r\nax2 = ax.twinx() \r\nax2.plot(dfm.index, dfm.mean_200.values, label='avg for 200s', color='#808080')\r\nax2.plot(dfm.index, dfm.mean_201.values, label='avg for 201s', color='#872d32')\r\nax.legend(loc='upper left')\r\nax2.legend(loc='lower right')\r\nax2.set_ylabel('average response times [ms]')\r\nax.xaxis.set_major_formatter( mdates.DateFormatter('%a, %d-%b'))\r\nplt.show()\r\n```\r\n\r\n**Actual outcome**\r\n\r\n\u003c!--The output produced by the above code, which may be a screenshot, console output, etc.--\u003e\r\n\r\n```\r\nax2.plot(dfm.index, dfm.mean_200.values, label='avg for 200s', color='#808080')\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/axes/_axes.py\", line 1667, in plot\r\n    self.add_line(line)\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/axes/_base.py\", line 1902, in add_line\r\n    self._update_line_limits(line)\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/axes/_base.py\", line 1924, in _update_line_limits\r\n    path = line.get_path()\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/lines.py\", line 1027, in get_path\r\n    self.recache()\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/lines.py\", line 670, in recache\r\n    x = _to_unmasked_float_array(xconv).ravel()\r\n  File \"/usr/local/lib/python3.7/site-packages/matplotlib/cbook/__init__.py\", line 1390, in _to_unmasked_float_array\r\n    return np.asarray(x, float)\r\n  File \"/usr/local/lib/python3.7/site-packages/numpy/core/_asarray.py\", line 85, in asarray\r\n    return array(a, dtype, copy=False, order=order)\r\nTypeError: float() argument must be a string or a number, not 'Timestamp'\r\n```\r\n\r\n**Expected outcome**\r\n\r\n\u003c!--A description of the expected outcome from the code snippet--\u003e\r\n![image](https://user-images.githubusercontent.com/7895513/73733085-99f78700-473b-11ea-9082-4ccb5deb6c28.png)\r\n\r\nThe image was generated with matplotlib version 3.1.0 it fails in 3.1.3\r\n\r\n**Matplotlib version**\r\n\u003c!--Please specify your platform and versions of the relevant libraries you are using:--\u003e\r\n  * Operating system: Works with 3.1.0 on Windows 10 and Linux (python docker)\r\n  * Matplotlib version: 3.1.0 / 3.1.3\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): agg\r\n  * Python version: 3.7\r\n  * Jupyter version (if applicable): nope\r\n  * Other libraries: pandas = 1.0.0 and 0.24.1 both work / fail\r\n\r\nAll installed from pip.\r\n\r\n","author":{"url":"https://github.com/icfly2","@type":"Person","name":"icfly2"},"datePublished":"2020-02-04T09:51:35.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":9},"url":"https://github.com/16405/matplotlib/issues/16405"}