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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Error with plot_date and agg backend: ValueError: ordinal must be \u003e= 1","articleBody":"When using plot_date in the agg backend I get the following error: ValueError: ordinal must be \u003e= 1. The problem does arise in matplotlib 1.5.1 (winpython 2.7.10.3), but not in 1.4.3 (winpython 2.7.10.2).\n\n```\nimport matplotlib as mpl\nimport matplotlib.pyplot as plt\nimport datetime\n\nplt.switch_backend('agg')\n#plt.switch_backend('qt4agg')\n\nx = [datetime.datetime(2013,12,i) for i in range(1, 11)]\ny = range(len(x))\nplt.plot_date(x,y)\n```\n\nStack trace:\n\n```\n  File \"D:/Python/untitled1.py\", line 19, in \u003cmodule\u003e\n    plt.plot_date(x,y)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\pyplot.py\", line 3173, in plot_date\n    data=data, **kwargs)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\__init__.py\", line 1812, in inner\n    return func(ax, *args, **kwargs)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axes\\_axes.py\", line 1494, in plot_date\n    ret = self.plot(x, y, fmt, **kwargs)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\__init__.py\", line 1812, in inner\n    return func(ax, *args, **kwargs)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axes\\_axes.py\", line 1424, in plot\n    for line in self._get_lines(*args, **kwargs):\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axes\\_base.py\", line 386, in _grab_next_args\n    for seg in self._plot_args(remaining, kwargs):\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axes\\_base.py\", line 364, in _plot_args\n    x, y = self._xy_from_xy(x, y)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axes\\_base.py\", line 197, in _xy_from_xy\n    bx = self.axes.xaxis.update_units(x)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axis.py\", line 1394, in update_units\n    self._update_axisinfo()\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axis.py\", line 1412, in _update_axisinfo\n    self.set_major_locator(info.majloc)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axis.py\", line 1513, in set_major_locator\n    self.stale = True\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\artist.py\", line 267, in stale\n    self.stale_callback(self, val)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\artist.py\", line 74, in _stale_axes_callback\n    self.axes.stale = val\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\artist.py\", line 267, in stale\n    self.stale_callback(self, val)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\figure.py\", line 56, in _stale_figure_callback\n    self.figure.stale = val\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\artist.py\", line 267, in stale\n    self.stale_callback(self, val)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\pyplot.py\", line 568, in _auto_draw_if_interactive\n    fig.canvas.draw_idle()\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\backend_bases.py\", line 2026, in draw_idle\n    self.draw(*args, **kwargs)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\backends\\backend_agg.py\", line 474, in draw\n    self.figure.draw(self.renderer)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\artist.py\", line 61, in draw_wrapper\n    draw(artist, renderer, *args, **kwargs)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\figure.py\", line 1159, in draw\n    func(*args)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\artist.py\", line 61, in draw_wrapper\n    draw(artist, renderer, *args, **kwargs)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axes\\_base.py\", line 2324, in draw\n    a.draw(renderer)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\artist.py\", line 61, in draw_wrapper\n    draw(artist, renderer, *args, **kwargs)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axis.py\", line 1106, in draw\n    ticks_to_draw = self._update_ticks(renderer)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axis.py\", line 949, in _update_ticks\n    tick_tups = [t for t in self.iter_ticks()]\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\axis.py\", line 892, in iter_ticks\n    majorLocs = self.major.locator()\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\dates.py\", line 1006, in __call__\n    self.refresh()\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\dates.py\", line 1026, in refresh\n    dmin, dmax = self.viewlim_to_dt()\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\dates.py\", line 770, in viewlim_to_dt\n    return num2date(vmin, self.tz), num2date(vmax, self.tz)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\dates.py\", line 419, in num2date\n    return _from_ordinalf(x, tz)\n  File \"C:\\WinPython-64bit-2.7.10.3\\python-2.7.10.amd64\\lib\\site-packages\\matplotlib\\dates.py\", line 271, in _from_ordinalf\n    dt = datetime.datetime.fromordinal(ix).replace(tzinfo=UTC)\nValueError: ordinal must be \u003e= 1\n```\n","author":{"url":"https://github.com/mvds314","@type":"Person","name":"mvds314"},"datePublished":"2016-02-18T09:08:27.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":20},"url":"https://github.com/6023/matplotlib/issues/6023"}