pivot table with aggfunc that combines two funtions

pandas, python

Solution

I think you need `lambda` - solution with pandas function `median` + `std` (is necessary change `ddof=0`, because by default `ddof=1` in pandas):

aggfunc=lambda x: x.median() - x.std(ddof=0)

what is same as:

aggfunc=lambda x: np.median(x) - np.std(x)

Sample:

data = pd.DataFrame({
    'Genename' : ['a','a','b','b', 'b', 'b'],
    'Mediancoverage' : [4, 1, 5, 3, 7, 5],
    'Componentnr' : [1,2,1,2,1,2],        
    })
print (data)
   Componentnr Genename  Mediancoverage
0            1        a               4
1            2        a               1
2            1        b               5
3            2        b               3
4            1        b               7
5            2        b               5

pivot=pd.pivot_table(data, 
                     columns='Genename', 
                     values='Mediancoverage',
                     index='Componentnr',
                     aggfunc=lambda x: x.median() - x.std(ddof=0))

print (pivot)
Genename     a  b
Componentnr      
1            4  5
2            1  3

pivot=pd.pivot_table(data, 
                     columns='Genename', 
                     values='Mediancoverage',
                     index='Componentnr',
                     aggfunc=lambda x: np.median(x) - np.std(x))

print (pivot)
Genename     a  b
Componentnr      
1            4  5
2            1  3

Problem

I want to create a pivot table with an aggfunc that combines two functions. I tried this ``` pivot=pd.pivot_table(data, columns='Genename', values=['Mediancoverage'],index='Componentnr', aggfunc=(np.median - np.std)) ``` and got this error: TypeError: unsupported operand type(s) for -: 'function' and 'function' I understand the problem but what is the solution?

Original source