Python Matplotlib，水平条形图（barh）是倒置的
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/34076177/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Matplotlib, horizontal bar chart (barh) is upside-down
提问by xpt
TL'DR, the vertical bar charts are shown in a conventional way -- things line up from left to right. However, when it is converted to horizontal bar chart (from barto barh), everything is upside-down. I.e., for a grouped bar chart, not only the order of the grouped bar is wrong, the order of the each group is wrong as well.
TL'DR，垂直条形图以传统方式显示 - 从左到右排列。但是，当它转换为水平条形图（从bar到barh）时，一切都是颠倒的。即，对于分组条形图，不仅分组条的顺序错误，每个组的顺序也错误。
For e.g., the graph from http://dwheelerau.com/2014/05/28/pandas-data-analysis-new-zealanders-and-their-sheep/
例如，来自http://dwheelerau.com/2014/05/28/pandas-data-analysis-new-zealanders-and-their-sheep/的图表
If you look closely, you will find that the the bar and legend are in reverse order -- Beef shows on top in legend but on bottom in the graph.
如果仔细观察，您会发现条形图和图例的顺序相反——牛肉显示在图例的顶部，但在图表的底部。
As the simplest demo, I changed kind='bar',to kind='barh',from this graph
https://plot.ly/pandas/bar-charts/#pandas-grouped-bar-chartand the result looks like this:
https://plot.ly/7/~xpt/
作为最简单的演示，我改变了kind='bar',对kind='barh',从该图
https://plot.ly/pandas/bar-charts/#pandas-grouped-bar-chart，结果如下所示：
https://plot.ly/7/ ~xpt/
I.e., the bars in the horizontal grouped bar chart is ordered upside-down.
即，水平分组条形图中的条形颠倒排列。
How to fix it?
如何解决？
EDIT:@Ajean, it is actually not only the order of the grouped bar is wrong, the order of the each group is wrong as well. The graph from Simple customization of matplotlib/pandas bar chart (labels, ticks, etc.)shows it clearly:
编辑：@Ajean，实际上不仅分组条的顺序错误，每个组的顺序也错误。来自matplotlib/pandas 条形图（标签、刻度等）的简单定制的图表清楚地显示了它：
We can see that the order is unconventional too, because people would expect the graph to be top-down, with "AAA" at the top, not the bottom.
我们可以看到顺序也是非常规的，因为人们希望图形是自上而下的，“AAA”在顶部，而不是底部。
If you search for "Excel upside-down", you will find people are complaining about this in Excel all over the places. The Microsoft Excel has a fix for it, do Matplotlib/Panda/Searborn/Ploty/etc has a fix for it?
如果你搜索“Excel颠倒”，你会发现到处都有人在Excel中抱怨这个。Microsoft Excel 有修复它，Matplotlib/Panda/Searborn/Ploty/etc 有修复它吗？
采纳答案by Andras Deak
I believe the joint wrong order of groups and subgroups boils down to a single feature: that the yaxis increases upwards, as in a usual plot. Try reversing the yaxis of your axes as in this pandas-less example:
我相信组和子组的联合错误顺序归结为一个特征：y轴向上增加，就像通常的情节一样。尝试反y转轴的轴，如这个无熊猫示例所示：
import numpy as np
import matplotlib.pyplot as plt
x=range(5)
y=np.random.randn(5)
#plot1: bar
plt.figure()
plt.bar(x,y)
#plot2: barh, wrong order
plt.figure()
plt.barh(x,y)
#plot3: barh with correct order: top-down y axis
plt.figure()
plt.barh(x,y)
plt.gca().invert_yaxis()
Specifically for pandas, pandas.DataFrame.plotand its various plotting submethods return a matplotlib axes object, so you can invert its y axis directly:
专门针对熊猫，pandas.DataFrame.plot其各种绘图子方法返回一个 matplotlib 轴对象，因此您可以直接反转其 y 轴：
ax = df.plot.barh() # or df.plot(), or similar
ax.invert_yaxis()
回答by CT Zhu
I will consider this to be a bug, i.e., the y position of the bars are not assigned correctly. The patch is however relatively simple:
我会认为这是一个错误，即条形的 y 位置未正确分配。然而，补丁相对简单：
This is only one right order of bars, and that is called..., the right order. Anything that is not the right order, is thus a buggy order. :p
这只是一种正确的条形顺序，这就是所谓的...，正确的顺序。因此，任何不正确的顺序都是错误的顺序。:p
In [63]:
print df
Total_beef_cattle Total_dairy_cattle Total_sheep Total_deer \
1994 0.000000 0.000000 0.000000 0.000000
2002 -11.025827 34.444950 -20.002034 33.858009
2003 -8.344764 32.882482 -20.041908 37.229441
2004 -11.895128 34.207998 -20.609926 42.707754
2005 -12.366101 32.506699 -19.379727 38.499840
Total_pigs Total_horses
1994 0.000000 0.000000
2002 -19.100637 11.811093
2003 -10.766476 18.504488
2004 -8.072078 13.376472
2005 -19.230733 -100.000000
In [64]:
ax = df.plot(kind='barh', sort_columns=True)
#Get the actual bars
bars = [item for item in ax.get_children() if isinstance(item, matplotlib.patches.Rectangle)]
bars = bars[:df.size]
#Reset the y positions for each bar
bars_y = [plt.getp(item, 'y') for item in bars]
for B, Y in zip(bars, np.flipud(np.array(bars_y).reshape(df.shape[::-1])).ravel()):
B.set_y(Y)
回答by alexsalo
General fix is simple:
一般修复很简单：
handles, labels = axis.get_legend_handles_labels()
# reverse to keep order consistent
axis.legend(reversed(handles), reversed(labels), loc='upper left')
回答by Philipp Schwarz
I believe the simplest solution for this problem is to reverse the pandas dataframe before plotting. For example:
我相信这个问题最简单的解决方案是在绘图之前反转熊猫数据框。例如：
df = df.iloc[::-1]
df.plot.barh(stacked=True);
In my opinion that is a bug in the pandas barh function. At least users should be able to pass an argument like reverse_order = True etc.
在我看来，这是 pandas barh 函数中的一个错误。至少用户应该能够传递像 reverse_order = True 等参数。
