ee.FeatureCollection.reduceColumns

החלת פונקציית צמצום על כל רכיב באוסף, באמצעות בוררים נתונים שקובעים את נתוני הקלט.

הפונקציה מחזירה מילון של תוצאות, עם שמות הפלט כמפתחות.

שימוש	החזרות
FeatureCollection.reduceColumns(reducer, selectors, weightSelectors)	מילון

ארגומנט	סוג	פרטים
זה: collection	FeatureCollection	האוסף לצבירה.
reducer	הפחתה	הפונקציה לצמצום שרוצים להחיל.
selectors	רשימה	בורר לכל קלט של פונקציית ה-reducer.
weightSelectors	רשימה, ברירת מחדל: null	בורר לכל קלט משוקלל של הפונקציה לצמצום.

דוגמאות

עורך הקוד (JavaScript)

// FeatureCollection of power plants in Belgium.
var fc = ee.FeatureCollection('WRI/GPPD/power_plants')
            .filter('country_lg == "Belgium"');

// Calculate mean of a single FeatureCollection property.
var propMean = fc.reduceColumns({
  reducer: ee.Reducer.mean(),
  selectors: ['gwh_estimt']
});
print('Mean of a single property', propMean);

// Calculate mean of multiple FeatureCollection properties.
var propsMean = 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.
var fuelWeights = 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) {
  return feature.set('weight', fuelWeights.getNumber(feature.get('fuel1')));
});

var weightedMean = fc.reduceColumns({
  reducer: ee.Reducer.mean(),
  selectors: ['gwh_estimt'],
  weightSelectors: ['weight']
});
print('Weighted mean of a single property', weightedMean);

הגדרת Python

מידע על Python API ועל שימוש ב-geemap לפיתוח אינטראקטיבי מופיע בדף Python Environment.

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"')

# 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.
def get_fuel(feature):
  return feature.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)