ValueError: x, y, and format string must not be None-CodePudding

I wanted to re-plot a graph with exponential moving averages, so I defined smooth curve below.

def smooth_curve(points, factor=0.8):
  smoothed_points = []
  for point in points:
     if smoothed_points:
       previous = smoothed_points[-1]
       smoothed_points.append(previous * factor   point * (1 - factor))
     else:
       smoothed_points.append(point)
  return

And I tried to plot with matplotlib.pyplot as plt

plt.plot(epochs, smooth_curve(acc), 'bo', label='smoothed training acc')

But I got the error below.

plt.plot(epochs, smooth_curve(acc), 'bo', label='smoothed training acc')
Traceback (most recent call last):

 Input In [119] in <cell line: 1>
 plt.plot(epochs, smooth_curve(acc), 'bo', label='smoothed training acc')

File C:\Anaconda3\lib\site-packages\matplotlib\pyplot.py:2757 in plot
 return gca().plot(

File C:\Anaconda3\lib\site-packages\matplotlib\axes\_axes.py:1632 in plot
 lines = [*self._get_lines(*args, data=data, **kwargs)]

File C:\Anaconda3\lib\site-packages\matplotlib\axes\_base.py:312 in __call__
 yield from self._plot_args(this, kwargs)

File C:\Anaconda3\lib\site-packages\matplotlib\axes\_base.py:459 in _plot_args
 raise ValueError("x, y, and format string must not be None")

ValueError: x, y, and format string must not be None

I checked the smooth_curve(acc) to be compiled successfully.

CodePudding user response：

You need to return smoothed_points variable after the function execution. If you just use return, the function will return a None null value causing issues with the rest of the code:

def smooth_curve(points, factor=0.8):
  smoothed_points = []
  for point in points:
     if smoothed_points:
       previous = smoothed_points[-1]
       smoothed_points.append(previous * factor   point * (1 - factor))
     else:
       smoothed_points.append(point)
  return smoothed_points