Python pandas idxmax for multiple indexes in a dataframe

Question

I have a series that looks like this:

            delivery
2007-04-26  706           23
2007-04-27  705           10
            706         1089
            708         


        

Answer 1

If you have the following dataframe (you can always reset the index if needed with : df = df.reset_index() :

  Date  Del_Count  Del_Nb
0  1/1      14      19   <
1           11      17
2  2/2      25      29   <
3           21      27
4           22      28
5  3/3      34      36
6           37      37
7           31      39   <

To find the max per Date and extract the relevant Del_Count you can use:

df = df.ix[df.groupby(['Date'], sort=False)['Del_Nb'].idxmax()][['Date','Del_Count','Del_Nb']]

Which would yeild:

 Date  Del_Count  Del_Nb
0  1/1         14      19
2  2/2         25      29
7  3/3         31      39