AI-generated Key Takeaways
-
The
iteratefunction applies an algorithm over a list, taking the current item and the result of the previous iteration as inputs. -
The function to be applied to each list element and an initial value for the first iteration are required arguments.
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The
iteratefunction returns an object which is the result of the final iteration.
| Usage | Returns |
|---|---|
List.
iterate
(function, first)
|
Object |
| Argument | Type | Details |
|---|---|---|
|
this:
list
|
List | |
function
|
Algorithm | |
first
|
Object |
Examples
Code Editor (JavaScript)
// This example uses the ee.List.iterate function to generate a series of // sequentially halved values. // Declare a list that will hold the series of sequentially halved values, // initialize it with the starting quantity. var quantityList = [ 1000 ]; // Define the number of iterations as a list sequence. var nSteps = ee . List . sequence ( 1 , 10 ); // Declare a function that takes the current element of the iteration list and // the returned result of the previous iteration as inputs. In this case, the // the function is returning an accumulating list of quantities that are reduced // by half at each iteration. var halfOfPrevious = function ( currentElement , previousResult ) { var previousQuantity = ee . Number ( ee . List ( previousResult ). get ( - 1 )); var currentQuantity = previousQuantity . divide ( 2 ); return ee . List ( previousResult ). add ( currentQuantity ); }; // Apply the function to the nSteps list, each element is an iteration. quantityList = ee . List ( nSteps . iterate ( halfOfPrevious , quantityList )); // Display the results. Note that step 0 is included for the initial value. print ( 'Steps in the iteration of halved quantities' , nSteps ); print ( 'Series of sequentially halved quantities' , quantityList ); print ( ui . Chart . array . values ({ array : quantityList , axis : 0 , xLabels : ee . List ([ 0 ]). cat ( nSteps ) }));
import ee import geemap.core as geemap
Colab (Python)
import matplotlib.pyplot as plt # This example uses the ee.List.iterate function to generate a series of # sequentially halved values. # Declare a list that will hold the series of sequentially halved values, # initialize it with the starting quantity. quantity_list = [ 1000 ] # Define the number of iterations as a list sequence. n_steps = ee . List . sequence ( 1 , 10 ) # Declare a function that takes the current element of the iteration list and # the returned result of the previous iteration as inputs. In this case, the # the function is returning an accumulating list of quantities that are reduced # by half at each iteration. def half_of_previous ( current_element , previous_result ): previous_quantity = ee . Number ( ee . List ( previous_result ) . get ( - 1 )) current_quantity = previous_quantity . divide ( 2 ) return ee . List ( previous_result ) . add ( current_quantity ) # Apply the function to the n_steps list, each element is an iteration. quantity_list = ee . List ( n_steps . iterate ( half_of_previous , quantity_list )) # Display the results. display ( 'Steps in the iteration of halved quantities' , n_steps ) display ( 'Series of sequentially halved quantities' , quantity_list ) quantity_list_client = quantity_list . getInfo () plt . scatter ( range ( len ( quantity_list_client )), quantity_list_client ) plt . show ()
