Cumulative sum in jq -

i have series of [timestamp, count] pairs in array , want compute cumulative sum @ each timestamp using jq. how that?

here sample data set:

[   [1431047957699, 1],   [1431047958269, 1],   [1431047958901, 1],   [1431047959147, -1],   [1431047960164, 1] ]

and expected result:

[1431047957699, 1], [1431047958269, 2], [1431047958901, 3], [1431047959147, 2], [1431047960164, 3]

is possible jq?

the following quite general (e.g. can used array of objects):

def accumulate(f):   reduce .[1:][] $row     ([.[0]];      . $x      | $x + [ $row | (f = ($x | .[length-1] | f) + ($row|f)  ) ] );  accumulate(.[1])

if using sufficiently recent version of jq, "$x | .[length-1]" can simplified "$x[-1]".

if jq has foreach, following variant can used. particularly appropriate if stream of values rather array wanted.

def accumulates(f):   foreach .[] $row     (0;      . + ($row | f) ;      . $x | $row | (f = $x));

usage:

for stream: accumulates(.[0])

for array: [accumulates(.[0])

Braziel