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.

Examples

Code Editor (JavaScript)

// A function to print the array for a selected pixel in the following examples.
function sampArrImg(arrImg) {
  var point = ee.Geometry.Point([-121, 42]);
  return arrImg.sample(point, 500).first().get('array');
}

// Create a 1D array image.
var arrayImg1D = ee.Image([1, 2, 3]).toArray();
print('1D array image (pixel)', sampArrImg(arrayImg1D));
// [1, 2, 3]

// Perform accumulation procedures along axes using ee.Reducer functions.
// Here we calculate the cumulative sum along the 0-axis for a 1D array.
var accumSum1DAx0 = arrayImg1D.arrayAccum(0, ee.Reducer.sum());
print('Cumulative sum along 0-axis', sampArrImg(accumSum1DAx0));
// [1, 3, 6]

// Create a 2D 3x3 array image.
var arrayImg2D = ee.Image([1, 2, 3, 4, 5, 6, 7, 8, 9]).toArray()
  .arrayReshape(ee.Image([3, 3]).toArray(), 2);
print('2D 3x3 array image (pixel)', sampArrImg(arrayImg2D));
// [[1, 2, 3],
//  [4, 5, 6],
//  [7, 8, 9]]

// Calculate the cumulative sum along the 0-axis for a 2D array.
var accumSum2DAx0 = arrayImg2D.arrayAccum(0, ee.Reducer.sum());
print('Cumulative sum along 0-axis', sampArrImg(accumSum2DAx0));
// [[ 1,  2,  3],
//  [ 5,  7,  9],
//  [12, 15, 18]]

// Calculate the cumulative sum along the 1-axis for a 2D array.
var accumSum2DAx1 = arrayImg2D.arrayAccum(1, ee.Reducer.sum());
print('Cumulative sum along 1-axis', sampArrImg(accumSum2DAx1));
// [[1,  3,  6],
//  [4,  9, 15],
//  [7, 15, 24]]

Python setup

See the Python Environment page for information on the Python API and using geemap for interactive development.

import ee
import geemap.core as geemap

Colab (Python)

# A function to print the array for a selected pixel in the following examples.
def samp_arr_img(arr_img):
  point = ee.Geometry.Point([-121, 42])
  return arr_img.sample(point, 500).first().get('array')

# Create a 1D array image.
array_img_1d = ee.Image([1, 2, 3]).toArray()
print('1D array image (pixel):', samp_arr_img(array_img_1d).getInfo())
# [1, 2, 3]

# Perform accumulation procedures along axes using ee.Reducer functions.
# Here we calculate the cumulative sum along the 0-axis for a 1D array.
accum_sum_1d_ax0 = array_img_1d.arrayAccum(0, ee.Reducer.sum())
print('Cumulative sum along 0-axis:', samp_arr_img(accum_sum_1d_ax0).getInfo())
# [1, 3, 6]

# Create a 2D 3x3 array image.
array_img_2d = ee.Image([1, 2, 3, 4, 5, 6, 7, 8, 9]).toArray().arrayReshape(
    ee.Image([3, 3]).toArray(),
    2)
print('2D 3x3 array image (pixel):', samp_arr_img(array_img_2d).getInfo())
# [[1, 2, 3],
#  [4, 5, 6],
#  [7, 8, 9]]

# Calculate the cumulative sum along the 0-axis for a 2D array.
accum_sum_2d_ax0 = array_img_2d.arrayAccum(0, ee.Reducer.sum())
print('Cumulative sum along 0-axis:', samp_arr_img(accum_sum_2d_ax0).getInfo())
# [[ 1,  2,  3],
#  [ 5,  7,  9],
#  [12, 15, 18]]

# Calculate the cumulative sum along the 1-axis for a 2D array.
accum_sum_2d_ax1 = array_img_2d.arrayAccum(1, ee.Reducer.sum())
print('Cumulative sum along 1-axis:', samp_arr_img(accum_sum_2d_ax1).getInfo())
# [[1,  3,  6],
#  [4,  9, 15],
#  [7, 15, 24]]