Calculate new value based on decreasing value

Question

Problem:

What\'d I like to do is step-by-step reduce a value in a Series by a continuously decreasing base figure.

I\'m not sur

Answer 1

This is probably not so performant but at the moment this is a Pandas way of doing this using rolling_apply:

In [53]:

ALLOWANCE = 100
def reduce(x):
    global ALLOWANCE
    # short circuit if we've already reached 0
    if ALLOWANCE == 0:
        return x
    val = max(0, x - ALLOWANCE)
    ALLOWANCE = max(0, ALLOWANCE - x)
    return val

pd.rolling_apply(values, window=1, func=reduce)
Out[53]:
0     0
1     0
2    20
3    30
dtype: float64

Or more simply:

In [58]:

values.apply(reduce)
Out[58]:
0     0
1     0
2    20
3    30
dtype: int64