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我正在尝试计算每个水域的水域和每个波段的统计数据，看看是否有季节性变化。

导出的 .csv 文件在加入之前只有列 ("GNIS_ID","AreaSqKm","waterArea")。我打印了变量 Join，它确实包含我需要的所有列。为什么它们没有显示在导出的 CSV 文件中？我错过了什么？

    var CollectMonth = ee.ImageCollection('LANDSAT/LC08/C01/T1_SR')
      .filterBounds(HI_poly)
      .sort('CLOUD_COVER')
      .filterDate('2014-01-01', '2014-01-30')
      .map(function(image){return image.clip(USGS_WBD)})  // clip the images by the;
      print(CollectMonth);

    // Calculate Water Area
    var waterThreshold = 324;

    var WaterAreaFunction = function(image){
      //add the water band to the image
      var water = image.select(['pixel_qa']).rename('water');
      //get pixels equal the threshold
      var water01 = water.eq(waterThreshold);
      //mask those pixels from the image
      image = image.updateMask(water01).addBands(water);

      var area = ee.Image.pixelArea();
      var waterArea = water01.multiply(area).rename('waterArea');

      image = image.addBands(waterArea);

      var stats = waterArea.reduceRegion({
        reducer: ee.Reducer.sum(), 
        geometry: USGS_WBD, 
        scale: 30,
      });

      return image.set(stats);
    };

    var l8Mosaic = CollectMonth.map(WaterAreaFunction).mosaic().multiply(0.0001);
    var l8Mosaic_area = l8Mosaic.divide(1000000)

    //statistics
    var WBD_area = l8Mosaic_area.reduceRegions({
      collection: USGS_WBD,
      reducer: ee.Reducer.sum(),
      scale: 30 // resolution
    }).select(["GNIS_ID","AreaSqKm","waterArea"]);
    print("area:",WBD_area);

    var WBD_value = l8Mosaic.select(["B1","B2","B3","B4","B5","B6","B7"])
                            .rename(["B1_mean","B2_mean","B3_mean","B4_mean","B5_mean","B6_mean","B7_mean"])
    var WBD_mean = WBD_value.reduceRegions({
      collection: USGS_WBD,
      reducer: ee.Reducer.mean(),
      scale: 30 // resolution
    }).select(["GNIS_ID","B1_mean","B2_mean","B3_mean","B4_mean","B5_mean","B6_mean","B7_mean"])
    print("mean:",WBD_mean);

    var WBD_value = l8Mosaic.select(["B1","B2","B3","B4","B5","B6","B7"])
                            .rename(["B1_median","B2_median","B3_median","B4_median","B5_median","B6_median","B7_median"])
    var WBD_median = WBD_value.reduceRegions({
      collection: USGS_WBD,
      reducer: ee.Reducer.median(),
      scale: 30 // resolution
    }).select(["GNIS_ID","B1_median","B2_median","B3_median","B4_median","B5_median","B6_median","B7_median"])
    print("median:",WBD_median);

    var WBD_value = l8Mosaic.select(["B1","B2","B3","B4","B5","B6","B7"])
                            .rename(["B1_min","B2_min","B3_min","B4_min","B5_min","B6_min","B7_min"])
    var WBD_min = WBD_value.reduceRegions({
      collection: USGS_WBD,
      reducer: ee.Reducer.min(),
      scale: 30 // resolution
    }).select(["GNIS_ID","B1_min","B2_min","B3_min","B4_min","B5_min","B6_min","B7_min"])
    print("min:",WBD_min);

    var WBD_value = l8Mosaic.select(["B1","B2","B3","B4","B5","B6","B7"])
                            .rename(["B1_max","B2_max","B3_max","B4_max","B5_max","B6_max","B7_max"])
    var WBD_max = WBD_value.reduceRegions({
      collection: USGS_WBD,
      reducer: ee.Reducer.max(),
      scale: 30 // resolution
    }).select(["GNIS_ID","B1_max","B2_max","B3_max","B4_max","B5_max","B6_max","B7_max"])
    print("max:",WBD_max);

    var WBD_value = l8Mosaic.select(["B1","B2","B3","B4","B5","B6","B7"])
                            .rename(["B1_WBD10","B2_WBD10","B3_WBD10","B4_WBD10","B5_WBD10","B6_WBD10","B7_WBD10"])
    var WBD10 = WBD_value.reduceRegions({
      collection: USGS_WBD,
      reducer: ee.Reducer.percentile([10]),
      scale: 30 // resolution
    }).select(["GNIS_ID","B1_WBD10","B2_WBD10","B3_WBD10","B4_WBD10","B5_WBD10","B6_WBD10","B7_WBD10"])
    print("WBD10:",WBD10);

    var WBD_value = l8Mosaic.select(["B1","B2","B3","B4","B5","B6","B7"])
                            .rename(["B1_WBD90","B2_WBD90","B3_WBD90","B4_WBD90","B5_WBD90","B6_WBD90","B7_WBD90"])
    var WBD90 = WBD_value.reduceRegions({
      collection: USGS_WBD,
      reducer: ee.Reducer.percentile([90]),
      scale: 30 // resolution
    }).select(["GNIS_ID","B1_WBD90","B2_WBD90","B3_WBD90","B4_WBD90","B5_WBD90","B6_WBD90","B7_WBD90"])
    print("WBD90:",WBD90);

    var WBD_value = l8Mosaic.select(["B1","B2","B3","B4","B5","B6","B7"])
                            .rename(["B1_std","B2_std","B3_std","B4_std","B5_std","B6_std","B7_std"])
    var WBD_std = WBD_value.reduceRegions({
      collection: USGS_WBD,
      reducer: ee.Reducer.stdDev(),
      scale: 30 // resolution
    }).select(["GNIS_ID","B1_std","B2_std","B3_std","B4_std","B5_std","B6_std","B7_std"])
    print("std:",WBD_std);

    var WBD_value = l8Mosaic.select(["B1","B2","B3","B4","B5","B6","B7"])
                            .rename(["B1_variance","B2_variance","B3_variance","B4_variance","B5_variance","B6_variance","B7_variance"])
    var WBD_variance = WBD_value.reduceRegions({
      collection: USGS_WBD,
      reducer: ee.Reducer.variance(),
      scale: 30 // resolution
    }).select(["GNIS_ID","B1_variance","B2_variance","B3_variance","B4_variance","B5_variance","B6_variance","B7_variance"])
    print("variance:",WBD_variance);


    // =============== Join ============================
    // Join two collection
    // Use an equals filter to define how the collections match.
    var filter = ee.Filter.equals({
      leftField: 'GNIS_ID',
      rightField: 'GNIS_ID'
    });

    // Define the join.
    var innerJoin = ee.Join.inner();

    // Apply the join.
    var Join = innerJoin.apply(WBD_area, WBD_mean, filter);
    Join = Join.map(function(pair) {
      var f1 = ee.Feature(pair.get('primary'));
      var f2 = ee.Feature(pair.get('secondary'));
      return f1.set(f2.toDictionary());
    });

    // Apply the join.
    var Join = innerJoin.apply(Join, WBD_median,filter);
    Join = Join.map(function(pair) {
      var f1 = ee.Feature(pair.get('primary'));
      var f2 = ee.Feature(pair.get('secondary'));
      return f1.set(f2.toDictionary());
    });

    // // Apply the join.
    var Join = innerJoin.apply(Join, WBD_min,filter);
    Join = Join.map(function(pair) {
      var f1 = ee.Feature(pair.get('primary'));
      var f2 = ee.Feature(pair.get('secondary'));
      return f1.set(f2.toDictionary());
    });

    // // Apply the join.
    var Join = innerJoin.apply(Join, WBD_max,filter);
    Join = Join.map(function(pair) {
      var f1 = ee.Feature(pair.get('primary'));
      var f2 = ee.Feature(pair.get('secondary'));
      return f1.set(f2.toDictionary());
    });

    // // Apply the join.
    var Join = innerJoin.apply(Join, WBD10,filter);
    Join = Join.map(function(pair) {
      var f1 = ee.Feature(pair.get('primary'));
      var f2 = ee.Feature(pair.get('secondary'));
      return f1.set(f2.toDictionary());
    });

    // // Apply the join.
    var Join = innerJoin.apply(Join, WBD90,filter);
    Join = Join.map(function(pair) {
      var f1 = ee.Feature(pair.get('primary'));
      var f2 = ee.Feature(pair.get('secondary'));
      return f1.set(f2.toDictionary());
    });

    // // Apply the join.
    var Join = innerJoin.apply(Join, WBD_std,filter);
    Join = Join.map(function(pair) {
      var f1 = ee.Feature(pair.get('primary'));
      var f2 = ee.Feature(pair.get('secondary'));
      return f1.set(f2.toDictionary());
    });

    // // Apply the join.
    var Join = innerJoin.apply(Join, WBD_variance,filter);
    Join = Join.map(function(pair) {
      var f1 = ee.Feature(pair.get('primary'));
      var f2 = ee.Feature(pair.get('secondary'));
      return f1.set(f2.toDictionary());
    });
    print(Join)

    // Export the FeatureCollection.
    Export.table.toDrive({
      collection: Join,
      description: 'Monthly_Lansat8_SR',
      fileFormat: 'CSV'
    });
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1 回答 1

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该代码对我有用。

但是您应该阅读有关组合减速器的信息。您可以使用这样的减速器跳过所有连接和大部分减少：

var reducer = ee.Reducer.mean()
                .combine({ reducer2: ee.Reducer.min(),  sharedInputs: true})
                .combine({ reducer2: ee.Reducer.max(),  sharedInputs: true})
                .combine({ reducer2: ee.Reducer.mean(),  sharedInputs: true})
                .combine({ reducer2: ee.Reducer.percentile([10, 90]),  sharedInputs: true})
                .combine({ reducer2: ee.Reducer.stdDev(),  sharedInputs: true})
                .combine({ reducer2: ee.Reducer.variance(),  sharedInputs: true});
于 2019-04-27T22:27:19.980 回答