Python bins 必须单调增加
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bins must increase monotonically
提问by Aurélien Vasseur
I just want to draw Matplotlib histograms from skimage.exposure but I get a ValueError: bins must increase monotonically.The original image comes from hereand here my code:
我只想从 skimage.exposure 绘制 Matplotlib 直方图，但我得到一个ValueError: bins must increase monotonically.原始图像来自这里和这里我的代码：
from skimage import io, exposure
import matplotlib.pyplot as plt
img = io.imread('img/coins_black_small.jpg', as_grey=True)
hist,bins=exposure.histogram(img)
plt.hist(bins,hist)
ValueError: bins must increase monotonically.
ValueError: bins 必须单调增加。
But the same error arises when I sort the bins values:
但是当我对 bin 值进行排序时会出现同样的错误：
import numpy as np
sorted_bins = np.sort(bins)
plt.hist(sorted_bins,hist)
ValueError: bins must increase monotonically.
ValueError: bins 必须单调增加。
I finally tried to check the bins values, but they seem sorted in my opinion (any advice for this kind of test would appreciated also):
我终于尝试检查 bins 值，但我认为它们似乎已排序（对于此类测试的任何建议也将不胜感激）：
if any(bins[:-1] >= bins[1:]):
print "bim"
No output from this.
没有输出。
Any suggestion on what happens?
I'm trying to learn Python, so be indulgent please. Here my install (on Linux Mint):
关于会发生什么的任何建议？
我正在尝试学习 Python，所以请放纵一下。这是我的安装（在 Linux Mint 上）：
- Python 2.7.13 :: Anaconda 4.3.1 (64-bit)
- Jupyter 4.2.1
- Python 2.7.13 :: Anaconda 4.3.1（64 位）
- Jupyter 4.2.1
回答by Ondro
Matplotlib histaccept data as first argument, not already binned counts. Use matplotlib barto plot it. Note that unlike numpy histogram, skimage exposure.histogramreturns the centers of bins.
Matplotlibhist接受数据作为第一个参数，而不是已经分箱的计数。使用 matplotlibbar绘制它。请注意，与 numpy 不同histogram， skimageexposure.histogram返回 bin 的中心。
width = bins[1] - bins[0]
plt.bar(bins, hist, align='center', width=width)
plt.show()
回答by ImportanceOfBeingErnest
The signature of plt.histis plt.hist(data, bins, ...). So you are trying to plug the already computed histogram as bins into the matplotlib histfunction. The histogram is of course not sorted and therefore the "bins must increase monotonically"-error is thrown.
的签名plt.hist是plt.hist(data, bins, ...)。所以你试图将已经计算的直方图作为 bin 插入到 matplotlibhist函数中。直方图当然没有排序，因此会抛出“垃圾箱必须单调增加”的错误。
While you could of course use plt.hist(hist, bins), it's questionable if histogramming a histogram is of any use. I would guess that you want to simply plot the result of the first histogramming.
虽然您当然可以使用plt.hist(hist, bins)，但对直方图进行直方图绘制是否有任何用处是值得怀疑的。我猜你想简单地绘制第一个直方图的结果。
Using a bar chart would make sense for this purpose:
为此目的，使用条形图是有意义的：
hist,bins=numpy.histogram(img)
plt.bar(bins[:-1], hist, width=(bins[-1]-bins[-2]), align="edge")
