Como solucionar error de pandas / matplotlib: raise ValueError(f'Fecha ordinal {x} converts to {dt}..

Problema:

Estás intentando trazar un pandas DataFrame o Series usando código como

plot_workaround.py

df.plot()

pero ves un mensaje de error como

matplotlib_date_ordinal_error.txt

Traceback (most recent call last):
  ...
  File "/usr/local/lib/python3.11/site-packages/matplotlib/figure.py", line 3390, in savefig
    self.canvas.print_figure(fname, **kwargs)
  File "/usr/local/lib/python3.11/site-packages/matplotlib/backend_bases.py", line 2164, in print_figure
    self.figure.draw(renderer)
  File "/usr/local/lib/python3.11/site-packages/matplotlib/artist.py", line 95, in draw_wrapper
    result = draw(artist, renderer, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/matplotlib/artist.py", line 72, in draw_wrapper
    return draw(artist, renderer)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/matplotlib/figure.py", line 3154, in draw
    mimage._draw_list_compositing_images(
  File "/usr/local/lib/python3.11/site-packages/matplotlib/image.py", line 132, in _draw_list_compositing_images
    a.draw(renderer)
  File "/usr/local/lib/python3.11/site-packages/matplotlib/artist.py", line 72, in draw_wrapper
    return draw(artist, renderer)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/matplotlib/axes/_base.py", line 3034, in draw
    self._update_title_position(renderer)
  File "/usr/local/lib/python3.11/site-packages/matplotlib/axes/_base.py", line 2969, in _update_title_position
    bb = ax.xaxis.get_tightbbox(renderer)
  File "/usr/local/lib/python3.11/site-packages/matplotlib/axis.py", line 1334, in get_tightbbox
    ticks_to_draw = self._update_ticks()
  File "/usr/local/lib/python3.11/site-packages/matplotlib/axis.py", line 1276, in _update_ticks
    major_labels = self.major.formatter.format_ticks(major_locs)
  File "/usr/local/lib/python3.11/site-packages/matplotlib/ticker.py", line 216, in format_ticks
    return [self(value, i) for i, value in enumerate(values)]
  File "/usr/local/lib/python3.11/site-packages/matplotlib/ticker.py", line 216, in <listcomp>
    return [self(value, i) for i, value in enumerate(values)]
  File "/usr/local/lib/python3.11/site-packages/matplotlib/dates.py", line 649, in __call__
    result = num2date(x, self.tz).strftime(self.fmt)
  File "/usr/local/lib/python3.11/site-packages/matplotlib/dates.py", line 543, in num2date
    return _from_ordinalf_np_vectorized(x, tz).tolist()
  File "/usr/local/lib/python3.11/site-packages/numpy/lib/function_base.py", line 2372, in __call__
    return self._call_as_normal(*args, **kwargs)
  File "/usr/local/lib/python3.11/site-packages/numpy/lib/function_base.py", line 2365, in _call_as_normal
    return self._vectorize_call(func=func, args=vargs)
  File "/usr/local/lib/python3.11/site-packages/numpy/lib/function_base.py", line 2455, in _vectorize_call
    outputs = ufunc(*inputs)
  File "/usr/local/lib/python3.11/site-packages/matplotlib/dates.py", line 362, in _from_ordinalf
    raise ValueError(f'Fecha ordinal {x} converts to {dt} (using

Solución

Este problema ha sido discutido en el Matplotlib Github y también pandas Github. Este problema ocurre si usas df.plot() pero luego configuras opciones de formato personalizadas para el eje x, para DataFrames con índice datetime.

Ahora mismo puedes evitar este bug ploteando manualmente los datos:

manual_plot_workaround.py

for column in df.columns:
    plt.plot(df.index.values, df[column].values, label=column)

en su lugar, pero ten en cuenta que podrías necesitar configurar algunas opciones de matplotlib tú mismo (que pandas de otro modo configuraría automáticamente) al trazar todo manualmente.