（重复）Margins=True 没有很好地总结 Pandas Pivot_Table

Question

对于以下代码片段和结果，由于

Margins=True

给出了一行的两个值的平均值，因此计算错误。有什么解释吗？

# Print the mean weekly_sales by department and type; fill missing values with 0s; sum all rows and cols

print(sales.pivot_table(values="weekly_sales", index="department", columns="type", fill_value=0,margins=True))

结果是：

type                A           B        All
department                                  
1           30961.725   44050.627  32052.467
2           67600.159  112958.527  71380.023
3           17160.003   30580.655  18278.391
4           44285.399   51219.654  44863.254
5           34821.011   63236.875  37189.000
...               ...         ...        ...
96          21367.043    9528.538  20337.608
97          28471.267    5828.873  26584.401
98          12875.423     217.428  11820.590
99            379.124       0.000    379.124
All         23674.667   25696.678  23843.950

我搜索了整个互联网，发现这个网站上有一个重复的主题。

Answer 1

这取决于什么需要：

#sample data
print (sales)
   weekly_sales  department type
0             4           1    A
1             7           2    A
2             4           2    B
3             3           1    B
4             1           1    A
5             2           2    A
6             3           2    B
7             5           1    B

默认聚合 - 平均值

print(sales.pivot_table(values="weekly_sales", 
                        index="department", 
                        columns="type", 
                        fill_value=0,
                        margins=True))
type          A     B    All
department                  
1           2.5  4.00  3.250
2           4.5  3.50  4.000
All         3.5  3.75  3.625

聚合 - 平均值

print(sales.pivot_table(values="weekly_sales", 
                        index="department",
                        columns="type",
                        aggfunc='mean', 
                        fill_value=0,
                        margins=True))
type          A     B    All
department                  
1           2.5  4.00  3.250
2           4.5  3.50  4.000
All         3.5  3.75  3.625

聚合 - 总和

print(sales.pivot_table(values="weekly_sales", 
                        index="department", 
                        columns="type", 
                        aggfunc='sum', 
                        fill_value=0,
                        margins=True))
type         A   B  All
department             
1            5   8   13
2            9   7   16
All         14  15   29

聚合平均值，所有列均按总和填充

out = sales.pivot_table(values="weekly_sales", 
                        index="department", 
                        columns="type", 
                        aggfunc='mean', 
                        fill_value=0)
out['All'] = out.sum(axis=1)
out.loc['All'] = out.sum()
print (out)
type          A    B   All
department                
1           2.5  4.0   6.5
2           4.5  3.5   8.0
All         7.0  7.5  14.5