AI-generated Key Takeaways
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Image.arrayAccumaccumulates elements of each array pixel along a given axis. -
The function calculates the reduction of elements in a pixel along the axis, up to and including the current position.
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It can be used to create cumulative sums or monotonically increasing sequences.
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The method takes the axis and an optional reducer as arguments, returning an Image.
| 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]]
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 () display ( '1D array image (pixel):' , samp_arr_img ( array_img_1d )) # [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 ()) display ( 'Cumulative sum along 0-axis:' , samp_arr_img ( accum_sum_1d_ax0 )) # [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 ) display ( '2D 3x3 array image (pixel):' , samp_arr_img ( array_img_2d )) # [[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 ()) display ( 'Cumulative sum along 0-axis:' , samp_arr_img ( accum_sum_2d_ax0 )) # [[ 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 ()) display ( 'Cumulative sum along 1-axis:' , samp_arr_img ( accum_sum_2d_ax1 )) # [[1, 3, 6], # [4, 9, 15], # [7, 15, 24]]
