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ee.FeatureCollection.map
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Maps an algorithm over a collection.
Returns the mapped collection.
Usage Returns FeatureCollection. map (algorithm, dropNulls )
Collection
Argument Type Details this: collection
Collection The Collection instance. algorithm
Function The operation to map over the images or features of the collection. A JavaScript function that receives an image or features and returns one. The function is called only once and the result is captured as a description, so it cannot perform imperative operations or rely on external state. dropNulls
Boolean, optional If true, the mapped algorithm is allowed to return nulls, and the elements for which it returns nulls will be dropped.
Examples
Code Editor (JavaScript)
// FeatureCollection of power plants in Belgium.
var fc = ee.FeatureCollection('WRI/GPPD/power_plants')
.filter('country_lg == "Belgium"');
// Function to convert power plant capacity from megawatts to gigawatts and
// add the value as a new feature property.
var mwToGw = function(feature) {
var megawatt = feature.getNumber('capacitymw');
var gigawatt = megawatt.divide(1000);
return feature.set('capacitygw', gigawatt);
};
// Apply the function to each feature in the collection.
fc = fc.map(mwToGw);
print('Note the new "capacitygw" property in each feature', fc);
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)
# FeatureCollection of power plants in Belgium.
fc = ee.FeatureCollection('WRI/GPPD/power_plants').filter(
'country_lg == "Belgium"')
# Function to convert power plant capacity from megawatts to gigawatts and
# add the value as a new feature property.
def mw_to_gw(feature):
megawatt = feature.getNumber('capacitymw')
gigawatt = megawatt.divide(1000)
return feature.set('capacitygw', gigawatt)
# Apply the function to each feature in the collection.
fc = fc.map(mw_to_gw)
print('Note the new "capacitygw" property in each feature:', fc.getInfo())
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Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License , and code samples are licensed under the Apache 2.0 License . For details, see the Google Developers Site Policies . Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2023-10-06 UTC.
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