ee.Image.arrayAccum

Accumulates elements of each array pixel along the given axis, by setting each element of the result array pixel to the reduction of elements in that pixel along the given axis, up to and including the current position on the axis. May be used to make a cumulative sum, a monotonically increasing sequence, etc.

Usage	Returns
Image.arrayAccum(axis, reducer)	Image

Argument	Type	Details
this: input	Image	Input image.
axis	Integer	Axis along which to perform the cumulative sum.
reducer	Reducer, default: null	Reducer to accumulate values. Default is SUM, to produce the cumulative sum of each vector along the given axis.