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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Cannot plot fully masked array against datetimes","articleBody":"### Bug report\r\n\r\n**Bug summary**\r\nCannot plot a fully masked array agaisnt an array of datetimes. A ValueError is raised for a seemingly unrelated reason. Surprisingly, matplotlib has no problem plotting a fully masked array by itself.\r\n\u003c!--A short 1-2 sentences that succinctly describes the bug--\u003e\r\n\r\n**Code for reproduction**\r\n\r\n```python\r\nimport matplotlib.pyplot as plt\r\nfrom datetime import datetime\r\nimport numpy as np\r\n\r\nx = np.array([\r\n    datetime(2017, 1, 1), \r\n    datetime(2017, 1, 2), \r\n    datetime(2017, 1, 3),\r\n    datetime(2017, 1, 4),\r\n    datetime(2017, 1, 5)\r\n])\r\n\r\ny = np.array([1,2,3,4,5])\r\nm = np.ma.masked_greater(y, 0)\r\n\r\nfig = plt.figure()\r\nax = fig.add_subplot(111)\r\nax.plot(x, m)\r\nplt.show()\r\n```\r\n\r\n**Actual outcome**\r\n\u003c!--The output produced by the above code, which may be a screenshot, console output, etc.--\u003e\r\n\r\n```\r\n[super big traceback, only showing the most recent to save space...]\r\n/usr/lib64/python3.5/dist-packages/matplotlib/dates.py in _from_ordinalf(x, tz)\r\n    258 \r\n    259     ix = int(x)\r\n--\u003e 260     dt = datetime.datetime.fromordinal(ix).replace(tzinfo=UTC)\r\n    261 \r\n    262     remainder = float(x) - ix\r\nValueError: ordinal must be \u003e= 1\r\n```\r\n\r\n**Expected outcome**\r\nAn empty graph. If you comment out `x` and don't plot against it, then matplotlib has no problem displaying an empty graph. It is only when you plot against a datetime array this is an issue.\r\n\u003c!--A description of the expected outcome from the code snippet--\u003e\r\n\u003c!--If this used to work in an earlier version of Matplotlib, please note the version it used to work on--\u003e\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: GNU/Linux\r\n  * Matplotlib version: 2.1.1\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): module://ipykernel.pylab.backend_inline\r\n  * Python version: 3.5.5\r\n  * Jupyter version (if applicable): 4.3.0\r\n  * Other libraries: numpy, datetime\r\n\r\n\u003c!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--\u003e\r\n\u003c!--If you installed from conda, please specify which channel you used if not the default--\u003e\r\n\r\n","author":{"url":"https://github.com/logdog","@type":"Person","name":"logdog"},"datePublished":"2018-05-29T19:05:23.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":13},"url":"https://github.com/11337/matplotlib/issues/11337"}