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ee.FeatureCollection.reduceColumns

  • FeatureCollection.reduceColumns applies a reducer to each element of a collection using specified selectors for input.

  • The method returns a dictionary of results, with keys corresponding to the output names.

  • The usage involves specifying a reducer, input selectors, and optionally weight selectors.

  • Arguments include the collection itself, the reducer, a list of selectors for inputs, and an optional list of weight selectors.

 Apply a reducer to each element of a collection, using the given selectors to determine the inputs.

Returns a dictionary of results, keyed with the output names.

UsageReturns
FeatureCollection.reduceColumns(reducer, selectors,weightSelectors)Dictionary
ArgumentTypeDetails
this:collectionFeatureCollectionThe collection to aggregate over.
reducerReducerThe reducer to apply.
selectorsListA selector for each input of the reducer.
weightSelectorsList, default: nullA selector for each weighted input of the reducer.

Examples

Code Editor (JavaScript)

// FeatureCollection of power plants in Belgium.varfc=ee.FeatureCollection('WRI/GPPD/power_plants').filter('country_lg == "Belgium"');// Calculate mean of a single FeatureCollection property.varpropMean=fc.reduceColumns({reducer:ee.Reducer.mean(),selectors:['gwh_estimt']});print('Mean of a single property',propMean);// Calculate mean of multiple FeatureCollection properties.varpropsMean=fc.reduceColumns({reducer:ee.Reducer.mean().repeat(2),selectors:['gwh_estimt','capacitymw']});print('Mean of multiple properties',propsMean);// Calculate weighted mean of a single FeatureCollection property. Add a fuel// source weight property to the FeatureCollection.varfuelWeights=ee.Dictionary({Wind:0.9,Gas:0.2,Oil:0.2,Coal:0.1,Hydro:0.7,Biomass:0.5,Nuclear:0.3});fc=fc.map(function(feature){returnfeature.set('weight',fuelWeights.getNumber(feature.get('fuel1')));});varweightedMean=fc.reduceColumns({reducer:ee.Reducer.mean(),selectors:['gwh_estimt'],weightSelectors:['weight']});print('Weighted mean of a single property',weightedMean);

Python setup

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

importeeimportgeemap.coreasgeemap

Colab (Python)

# FeatureCollection of power plants in Belgium.fc=ee.FeatureCollection('WRI/GPPD/power_plants').filter('country_lg == "Belgium"')# Calculate mean of a single FeatureCollection property.prop_mean=fc.reduceColumns(**{'reducer':ee.Reducer.mean(),'selectors':['gwh_estimt']})display('Mean of a single property:',prop_mean)# Calculate mean of multiple FeatureCollection properties.props_mean=fc.reduceColumns(**{'reducer':ee.Reducer.mean().repeat(2),'selectors':['gwh_estimt','capacitymw']})display('Mean of multiple properties:',props_mean)# Calculate weighted mean of a single FeatureCollection property. Add a fuel# source weight property to the FeatureCollection.defget_fuel(feature):returnfeature.set('weight',fuel_weights.getNumber(feature.get('fuel1')))fuel_weights=ee.Dictionary({'Wind':0.9,'Gas':0.2,'Oil':0.2,'Coal':0.1,'Hydro':0.7,'Biomass':0.5,'Nuclear':0.3})fc=fc.map(get_fuel)weighted_mean=fc.reduceColumns(**{'reducer':ee.Reducer.mean(),'selectors':['gwh_estimt'],'weightSelectors':['weight']})display('Weighted mean of a single property:',weighted_mean)

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Last updated 2023-10-06 UTC.