极坐标图：TypeError：“numpy.float64”对象不能被解释为索引

Posted 2023-03-27

【中文标题】极坐标图：TypeError：“numpy.float64”对象不能被解释为索引

【英文标题】：Polar Plot: TypeError: 'numpy.float64' object cannot be interpreted as an index

【发布时间】：2021-03-03 05:58:44

【问题描述】：

我怀疑这个问题的答案是“不要使用 Matplotlib 极坐标图”。

我正在尝试生成极坐标图similar to this example plot 并将图表写入文件。

"""
Demo of a line plot on a polar axis.
"""
import numpy as np
import matplotlib.pyplot as plt


r = np.arange(0, 3.0, 0.01)
theta = 2 * np.pi * r

ax = plt.subplot(111, polar=True)
ax.plot(theta, r, color='r', linewidth=3)
ax.set_rmax(2.0)
ax.grid(True)

ax.set_title("A line plot on a polar axis", va='bottom')
plt.savefig("/path/to/file/plot.png")

当使用show() 时，图形将被绘制，并且在shell 中出现回溯。使用savefig() 时，回溯会导致savefig() 操作在未完成的情况下退出——因此不会写入文件。这似乎是matplotlib 内部的错误，仅将脚本转换为删除numpy 是不够的，因为savefig() 正在使用numpy 进行极坐标绘图。 此示例在早期版本的 Mac OS 上运行良好（可能是早期版本的 numpy ）。

我已经尝试过什么

捕获TypeError。 将r 和theta 转换为标准元组并从脚本中删除numpy。

我不能尝试的事情

从 Matplotlib show() 视图窗口保存无花果（必须使用 savefig()）。 升级 Python 升级 Matplotlib 降级 numpy Mac OS 降级

我运气不好？

Mac OS 10.15.7 Python 2.7 Matplotlib 1.3.1 numpy 1.16.6

更新： 上面的脚本在不同的机器上运行良好，这个版本的 numpy：Mac OS 10.15.7 Python 2.7 Matplotlib 1.3.1 numpy 1.8.0rc1

更新 2： 这是所有冗长的追溯。

Traceback (most recent call last):
  File "untitled text 7", line 20, in <module>
    plt.savefig('/Path/To/File/plot.png')
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/pyplot.py", line 561, in savefig
    return fig.savefig(*args, **kwargs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/figure.py", line 1421, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/backend_bases.py", line 2220, in print_figure
    **kwargs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/backend_bases.py", line 1962, in print_png
    return agg.print_png(*args, **kwargs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/backends/backend_agg.py", line 505, in print_png
    FigureCanvasAgg.draw(self)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/backends/backend_agg.py", line 451, in draw
    self.figure.draw(self.renderer)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/artist.py", line 55, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/figure.py", line 1034, in draw
    func(*args)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/artist.py", line 55, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/axes.py", line 2086, in draw
    a.draw(renderer)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/artist.py", line 55, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/axis.py", line 1096, in draw
    tick.draw(renderer)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/artist.py", line 55, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/axis.py", line 234, in draw
    self.gridline.draw(renderer)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/artist.py", line 55, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/lines.py", line 550, in draw
    tpath, affine = transf_path.get_transformed_path_and_affine()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/transforms.py", line 2562, in get_transformed_path_and_affine
    self._revalidate()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/transforms.py", line 2539, in _revalidate
    self._transform.transform_path_non_affine(self._path)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/transforms.py", line 2230, in transform_path_non_affine
    self._a.transform_path(path))
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/transforms.py", line 2227, in transform_path_non_affine
    return self._a.transform_path_non_affine(path)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/transforms.py", line 2230, in transform_path_non_affine
    self._a.transform_path(path))
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/projections/polar.py", line 72, in transform_path_non_affine
    ipath = path.interpolated(path._interpolation_steps)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/path.py", line 553, in interpolated
    vertices = simple_linear_interpolation(self.vertices, steps)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python/matplotlib/cbook.py", line 1711, in simple_linear_interpolation
    result = np.zeros(new_shape, a.dtype)
TypeError: 'numpy.float64' object cannot be interpreted as an index

【问题讨论】：

numpy 的当前版本是 1.19，但正在放弃对 Py.2.7 的支持。 Matplotlib 是 3.3.2。所以你使用的是旧版本。 numpy 已收紧其索引规则。浮点数（例如 2.3）作为索引没有意义，但旧版本允许您使用 2.0 而不是 2。如果错误是由 matplotlib 中的草率引起的，唯一的解决方法可能是获得正确的版本组合。

我们通常要求提供完整的回溯，以便更好地了解问题所在。但这可能隐藏在 matplotlib 调用中，因此可能很难破译。

@hpaulj - 谢谢。不幸的是，这是一个项目要分布在广泛的机器上，这些机器运行的版本与描述的一样旧（甚至更旧）。将其复制到回溯中。它很长，但为了完整起见，我将继续添加它。

【参考方案1】：

在新的numpy 中，最后一个表达式会产生各种结果或错误：

In [108]: np.zeros(10)
Out[108]: array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0.])

In [109]: np.zeros(10.)
Traceback (most recent call last):
  File "<ipython-input-109-6c3d535444cc>", line 1, in <module>
    np.zeros(10.)
TypeError: 'float' object cannot be interpreted as an integer

In [111]: np.zeros(np.array(10.))
Traceback (most recent call last):
  File "<ipython-input-111-4250f3d71116>", line 1, in <module>
    np.zeros(np.array(10.))
TypeError: only integer scalar arrays can be converted to a scalar index

In [112]: np.zeros(np.array([10.]))
Traceback (most recent call last):
  File "<ipython-input-112-e10bfdd4bb4f>", line 1, in <module>
    np.zeros(np.array([10.]))
TypeError: 'numpy.float64' object cannot be interpreted as an integer

【讨论】：

感谢调查。经过大量研究，似乎唯一的制胜法宝就是不玩。看来我得想出一个替代解决方案了。