Iterate an algorithm over a list. The algorithm is expected to take two objects, the current list item, and the result from the previous iteration or the value of first for the first 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)
}));