熊猫：排序枢轴表

Question

Just trying out pandas for the first time, and I am trying to sort a pivot table first by an index, then by the values in a series.

So far I've tried:

table = pivot_table(sheet1, values='Value', rows=['A','B'], aggfunc=np.sum)

# Sorts by value ascending, can't change to descending
table.copy().sort()
table

# The following gives me the correct ordering in values, but ignores index 
sorted_table = table.order(ascending=False)
sorted_table

# The following brings me back to the original ordering
sorted_table = table.order(ascending=False)
sorted_table2 = sorted_table.sortlevel(0)
sorted_table2

What's the correct way to sort a pivot table by index then value?

Answer 1

Here is a solution that may do what you want:

key1 = table.index.labels[0]
key2 = table.rank(ascending=False)

# sort by key1, then key2
sorter = np.lexsort((key2, key1))

sorted_table = table.take(sorter)

The result would look like this:

In [22]: table
Out[22]: 
A    B    
bar  one      0.698202
     three    0.801326
     two     -0.205257
foo  one     -0.963747
     three    0.120621
     two      0.189623
Name: C

In [23]: table.take(sorter)
Out[23]: 
A    B    
bar  three    0.801326
     one      0.698202
     two     -0.205257
foo  two      0.189623
     three    0.120621
     one     -0.963747
Name: C

This would be good to build into pandas as an API method. Not sure what it should look like though.