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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Datetime plot fails with 'Agg' backend in interactive mode","articleBody":"\u003c!--To help us understand and resolve your issue, please fill out the form to the best of your ability.--\u003e\r\n\u003c!--You can feel free to delete the sections that do not apply.--\u003e\r\n\r\n### Bug report\r\n\r\n**Bug summary**\r\n\r\n\u003c!--A short 1-2 sentences that succinctly describes the bug--\u003e\r\nI try to plot the time series data, and the X-axis represents the datetime. The code succeeds when use the 'Qt5Agg' backend, but fails when use the 'Agg' backend\r\n**Code for reproduction**\r\nThe example code based on the matplotlib tutorials(https://matplotlib.org/3.1.1/gallery/ticks_and_spines/date_concise_formatter.html).\r\nWhen use the 'Qt5Agg' backend, the code works well.(To show my issue, I use the `python` instead of `ipython`, because the `ipython` will use 'Qt5Agg' backend as default in my ENV)\r\n```python\r\nPython 3.6.8 (default, Oct  7 2019, 12:59:55) \r\n[GCC 8.3.0] on linux\r\nType \"help\", \"copyright\", \"credits\" or \"license\" for more information.\r\n\u003e\u003e\u003e import datetime\r\n\u003e\u003e\u003e import matplotlib.pyplot as plt\r\n\u003e\u003e\u003e import matplotlib.dates as mdates\r\n\u003e\u003e\u003e import numpy as np\r\n\u003e\u003e\u003e base = datetime.datetime(2005, 2, 1)\r\n\u003e\u003e\u003e dates = np.array([base + datetime.timedelta(hours=(2 * i)) for i in range(732)])\r\n\u003e\u003e\u003e np.random.seed(19680801)\r\n\u003e\u003e\u003e N = len(dates)\r\n\u003e\u003e\u003e y = np.cumsum(np.random.randn(N))\r\n\u003e\u003e\u003e import matplotlib\r\n\u003e\u003e\u003e matplotlib.get_backend()\r\n'Qt5Agg'\r\n\u003e\u003e\u003e plt.plot(dates,y)\r\n[\u003cmatplotlib.lines.Line2D object at 0x7f621c039828\u003e]\r\n```\r\nAnd I get the expected figure.\r\n![Figure_1](https://user-images.githubusercontent.com/23021820/66695710-7aa19d80-ecf7-11e9-9de0-654e38389b42.png)\r\nBut when I use 'Agg' backend, the code fails.\r\n```python\r\nPython 3.6.8 (default, Oct  7 2019, 12:59:55) \r\n[GCC 8.3.0] on linux\r\nType \"help\", \"copyright\", \"credits\" or \"license\" for more information.\r\n\u003e\u003e\u003e import matplotlib\r\n\u003e\u003e\u003e matplotlib.use('Agg')\r\n\u003e\u003e\u003e matplotlib.get_backend()\r\n'agg'\r\n\u003e\u003e\u003e import datetime\r\n\u003e\u003e\u003e import matplotlib.pyplot as plt\r\n\u003e\u003e\u003e import matplotlib.dates as mdates\r\n\u003e\u003e\u003e import numpy as np\r\n\u003e\u003e\u003e base = datetime.datetime(2005, 2, 1)\r\n\u003e\u003e\u003e dates = np.array([base + datetime.timedelta(hours=(2 * i)) for i in range(732)])\r\n\u003e\u003e\u003e N = len(dates)\r\n\u003e\u003e\u003e np.random.seed(19680801)\r\n\u003e\u003e\u003e y = np.cumsum(np.random.randn(N))\r\n\u003e\u003e\u003e plt.plot(dates,y)\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/pyplot.py\", line 2795, in plot\r\n    is not None else {}), **kwargs)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axes/_axes.py\", line 1666, in plot\r\n    lines = [*self._get_lines(*args, data=data, **kwargs)]\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py\", line 225, in __call__\r\n    yield from self._plot_args(this, kwargs)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py\", line 391, in _plot_args\r\n    x, y = self._xy_from_xy(x, y)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py\", line 243, in _xy_from_xy\r\n    bx = self.axes.xaxis.update_units(x)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axis.py\", line 1498, in update_units\r\n    self._update_axisinfo()\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axis.py\", line 1516, in _update_axisinfo\r\n    self.set_major_locator(info.majloc)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axis.py\", line 1651, in set_major_locator\r\n    self.stale = True\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/artist.py\", line 230, in stale\r\n    self.stale_callback(self, val)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/artist.py\", line 51, in _stale_axes_callback\r\n    self.axes.stale = val\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/artist.py\", line 230, in stale\r\n    self.stale_callback(self, val)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/figure.py\", line 51, in _stale_figure_callback\r\n    self.figure.stale = val\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/artist.py\", line 230, in stale\r\n    self.stale_callback(self, val)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/pyplot.py\", line 589, in _auto_draw_if_interactive\r\n    fig.canvas.draw_idle()\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/backend_bases.py\", line 1907, in draw_idle\r\n    self.draw(*args, **kwargs)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/backends/backend_agg.py\", line 388, in draw\r\n    self.figure.draw(self.renderer)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/artist.py\", line 38, in draw_wrapper\r\n    return draw(artist, renderer, *args, **kwargs)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/figure.py\", line 1709, in draw\r\n    renderer, self, artists, self.suppressComposite)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/image.py\", line 135, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/artist.py\", line 38, in draw_wrapper\r\n    return draw(artist, renderer, *args, **kwargs)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axes/_base.py\", line 2647, in draw\r\n    mimage._draw_list_compositing_images(renderer, self, artists)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/image.py\", line 135, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/artist.py\", line 38, in draw_wrapper\r\n    return draw(artist, renderer, *args, **kwargs)\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axis.py\", line 1203, in draw\r\n    ticks_to_draw = self._update_ticks()\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axis.py\", line 1079, in _update_ticks\r\n    major_locs = self.get_majorticklocs()\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/axis.py\", line 1324, in get_majorticklocs\r\n    return self.major.locator()\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/dates.py\", line 1431, in __call__\r\n    self.refresh()\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/dates.py\", line 1451, in refresh\r\n    dmin, dmax = self.viewlim_to_dt()\r\n  File \"/home/fanxp/.local/lib/python3.6/site-packages/matplotlib/dates.py\", line 1202, in viewlim_to_dt\r\n    .format(vmin))\r\nValueError: view limit minimum 0.0 is less than 1 and is an invalid Matplotlib date value. This often happens if you pass a non-datetime value to an axis that has datetime units\r\n\u003e\u003e\u003e\r\n```\r\nSo, how can I resolve this issue? Thanks!\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: ubuntu 18.04\r\n  * Matplotlib version: 3.1.1\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): agg\r\n  * Python version: 3.6.8\r\n  * Jupyter version (if applicable):\r\n  * Other libraries: numpy 1.17.2\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\nI use `pip` to install numpy and matplotlib, and I use the system's python3\r\n","author":{"url":"https://github.com/fanxinping","@type":"Person","name":"fanxinping"},"datePublished":"2019-10-12T06:05:28.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":13},"url":"https://github.com/15409/matplotlib/issues/15409"}