Why can't I apply shift from within a pandas function?

Question

I am trying to build a function that uses .shift() but it is giving me an error. Consider this:

In [40]:

data={\'level1\':[20,19,20,21,25,29,30,31,30,29,31]         


        

Answer 1

Try passing the frame to the function, rather than using apply (I am not sure why apply doesn't work, even column-wise):

def f(x):
    x.level1 
    return x.level1 + x.level1.shift(1)

f(frame)

returns:

2014-12-01   NaN
2014-12-02    39
2014-12-03    39
2014-12-04    41
2014-12-05    46
2014-12-06    54
2014-12-07    59
2014-12-08    61
2014-12-09    61
2014-12-10    59
2014-12-11    60
Freq: D, Name: level1, dtype: float64