Rtrader - 3 months ago 22

Python Question

What I want to do is generate a numpy array that is the cumulative sum of another numpy array given a certain window.

For example, given an array

`[1,2,3,4,5,6,7,8,9,10,11,12]`

`[1,3,6,9,12,15,18,21,24,27,30,33]`

Answer

```
In [42]: lis=[1,2,3,4,5,6,7,8,9,10,11,12]
In [43]: w=3 #window size
In [44]: [sum(lis[i-(w-1):i+1]) if i>(w-1) else sum(lis[:i+1]) for i in range(len(lis))]
Out[44]: [1, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33]
In [45]: w=4
In [46]: [sum(lis[i-(w-1):i+1]) if i>(w-1) else sum(lis[:i+1]) for i in range(len(lis))]
Out[46]: [1, 3, 6, 10, 14, 18, 22, 26, 30, 34, 38, 42]
```

for python 2.4 or less, change the ternary operator:

`(falseValue, trueValue)[condition]`

instead of `trueValue if condition else falseValue`

```
[(sum(lis[:i+1]),sum(lis[i-(w-1):i+1]))[i>(w-1)] for i in range(len(lis))]
```