Reference · Vectors

vec.rolling_sum

vec.rolling_sum(list, int) -> list

What it does

The sum of each run of window neighbouring items, as a list of floats. Only full windows count, so the result has len(xs) - window + 1 items: the first is the sum of the first window items, the last the sum of the last window.

Examples

print(vec.rolling_sum([1, 2, 3, 4, 5], 3))print(vec.rolling_sum([1, 2, 3], 2))

[6.0, 9.0, 12.0][3.0, 5.0]

Edge cases

• The result is floats even for ints: [3.0, 5.0], not [3, 5].
• A window of 1 is the list itself, as floats; a window as long as the list gives one item, the total.
• A window longer than the list gives the empty list; so do the empty list and null.
• The sums are compensated: [0.1, 0.2] with a window of 2 gives 0.30000000000000004, the float nearest 0.3 after one rounding, the same as 0.1 + 0.2.

print(vec.rolling_sum([1, 2, 3], 1), vec.rolling_sum([1, 2, 3], 3))print(vec.rolling_sum([1, 2, 3], 4), vec.rolling_sum([], 2), vec.rolling_sum(null, 1))print(vec.rolling_sum([0.1, 0.2, 0.3], 2))

[1.0, 2.0, 3.0] [6.0][] [] [][0.30000000000000004, 0.5]

Errors

A window below 1, a missing window, a window that is not an int, an item that is not an int or a float, or a first argument that is not a list are runtime errors, not error values.

print(vec.rolling_sum([1, "a"], 1))

line 1: `vec.rolling_sum` expects a list of numbers, but item 1 is str

print(vec.rolling_sum([1, 2], 1.5))

line 1: `vec.rolling_sum` expects an int as argument 2, got float

Chaining

The best three days in a row, and where they start:

let sales = [3, 5, 4, 6, 8, 2]let threes = sales | vec.rolling_sum(3)print(threes)print(max(threes), vec.argmax(threes))

[12.0, 15.0, 18.0, 16.0]18.0 2

See also

vec.rolling_mean, vec.cumsum, sum, vec.argmax

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