python - 尝试使用 matplotlib 绘制大型数组时出现内存错误

Question

我想绘制一个包含 2000 万个对象的数组，我有 8GB 内存，但在运行以下行时仍然出现以下错误:

import matplotlib.pyplot as plt
import numpy as np

d = np.arange(200000000)
plt.plot(d)
plt.show()

错误:

Traceback (most recent call last):
...
  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 317, in _grab_next_args
    for seg in self._plot_args(remaining, kwargs):
  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 292, in _plot_args
    x = np.arange(y.shape[0], dtype=float)
MemoryError

Answer 1

由于显示器和绘图仪的物理限制，无论如何您都无法绘制 20,000,000 个点。因此，您可以通过对其进行采样或使用切片来减少数组:

>>> m = 20000000
>>> a = np.arange(m)
>>> n = 100 # <- reducing to 100 points
>>> s = m/n # <- size of slices to compress
>>> reduced = []
>>> for i in xrange(n):
...     slice = a[i*s:(i+1)*s]
...     reduced.append(np.mean(slice))
>>> reduced
[99999.5, 299999.5, ..., 19699999.5, 19899999.5]

.. 假设 np.mean 对您正在绘制的对象有意义。