Matplotlib失败，返回ValueError:无法将浮点NaN转换为整数

Question

我在seaborn库中遇到了一个奇怪的问题。当为数值从非常低到非常高的数据生成条形图时，例如：

job      duration type
0    1  83066.639344    A
1    2    820.700000    B

它失败了：

ValueError: cannot convert float NaN to integer

这看起来像是matplotlib中的一个错误，重复了"pyplot.savefig失败，返回ValueError：无法将浮点NaN转换为整数"。后者尚未解决。有解决办法吗？

以下是重现问题的最小工作示例：

#!/usr/bin/env python3
import matplotlib.pyplot as plt
import pandas as pd
import seaborn as sns
d = {'job': [1, 2]),
'duration': [83066.639344, 820.700000],
'type': ['A', 'B']}
df = pd.DataFrame(d)
plot = sns.catplot(x="duration", y="job", data=df, hue='type',
color="b", kind="bar", height=3, aspect=4)
ax = plot.axes.flat[0]
for p in plt.gca().patches:
ax.text(p.get_width(),
p.get_y() + p.get_height() / 2,
p.get_width())
plot.savefig("barplot.png")

一些观察：

1. 如果我不区分"类型"(不使用hue='type'(，则不会出现问题

以下是完整的堆栈：

posx and posy should be finite values
posx and posy should be finite values
/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/numpy/core/fromnumeric.py:83: RuntimeWarning: invalid value encountered in reduce
return ufunc.reduce(obj, axis, dtype, out, **passkwargs)
posx and posy should be finite values
posx and posy should be finite values
posx and posy should be finite values
Traceback (most recent call last):
File "/Users/dzieciou/projects/example/gocd/reproduce.py", line 31, in <module>
plot.savefig("barplot.png")
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/seaborn/axisgrid.py", line 37, in savefig
self.fig.savefig(*args, **kwargs)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/figure.py", line 2094, in savefig
self.canvas.print_figure(fname, **kwargs)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/backend_bases.py", line 2075, in print_figure
**kwargs)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/backends/backend_agg.py", line 510, in print_png
FigureCanvasAgg.draw(self)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/backends/backend_agg.py", line 402, in draw
self.figure.draw(self.renderer)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/artist.py", line 50, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/figure.py", line 1649, in draw
renderer, self, artists, self.suppressComposite)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/image.py", line 138, in _draw_list_compositing_images
a.draw(renderer)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/artist.py", line 50, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/axes/_base.py", line 2610, in draw
mimage._draw_list_compositing_images(renderer, self, artists)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/image.py", line 138, in _draw_list_compositing_images
a.draw(renderer)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/artist.py", line 50, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/axis.py", line 1185, in draw
ticks_to_draw = self._update_ticks(renderer)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/axis.py", line 1023, in _update_ticks
tick_tups = list(self.iter_ticks())  # iter_ticks calls the locator
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/axis.py", line 967, in iter_ticks
majorLocs = self.major.locator()
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/ticker.py", line 1985, in __call__
return self.tick_values(vmin, vmax)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/ticker.py", line 1993, in tick_values
locs = self._raw_ticks(vmin, vmax)
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/ticker.py", line 1932, in _raw_ticks
nbins = np.clip(self.axis.get_tick_space(),
File "/Users/dzieciou/virtualenvs/seaborn/lib/python3.7/site-packages/matplotlib/axis.py", line 2543, in get_tick_space
return int(np.floor(length / size))
ValueError: cannot convert float NaN to integer

Answer 1

请注意，这既不是真正的bug，也与链接的bug无关，后者确实已修复。

不过，有人可能会认为，在nan坐标下绘制文本时，应该有更好的错误消息。

在查看错误之前，您的代码中似乎还有另一个问题，即将文本的x坐标设置为条形图的宽度。它们通常是不相关的，您可能打算使用p.get_x()。

现在有两个选项：

1.不要将文本放置在无效坐标处

import numpy as np
import matplotlib.pyplot as plt
import pandas as pd
import seaborn as sns
d = {'job': list(range(1, 3)),
'duration': [83066.639344, 820.700000],
'type': ['A', 'B']}
df = pd.DataFrame(d)
plot = sns.catplot(x="duration", y="job", data=df, hue='type',
color="b", kind="bar", height=3, aspect=4)
ax = plot.axes.flat[0]
for p in plt.gca().patches:
height = np.nan_to_num(p.get_height(), 0)
ax.text(p.get_x(), p.get_y() + height/2., "My text")
plot.savefig("barplot.png")
plt.show()

2.不要使用bbox_inches="tight"

如果您想保持代码的原样，可以通过不在seaborn的savefig中设置bbox_inches="tight"选项来解决此问题。

plot.savefig("barplot.png", bbox_inches=None)

或者使用matplotlib的savefig选项

plot.fig.savefig("barplot.png")