使用Google Earth Engine制作作物时间序列变化曲线

//Sentinel2数据制作时间序列NDVI，没有进行云量筛选，有待完善

//定义图表中不同作物类型的颜色
var COLOR = {
DADOU: '7FFF00',
GAOLIANG: 'ff0000',
YUMI: '0000ff'
};
//定义感兴趣区
var gaoliang = ee.Feature(
ee.Geometry.Rectangle(123.269, 48.0495, 123.272, 48.0511),
{label: 'Gaoliang'});
var yumi = ee.Feature(
ee.Geometry.Rectangle(123.2892, 48.0599, 123.2907, 48.0582),
{label: 'Yumi'});
var dadou = ee.Feature(
ee.Geometry.Rectangle(123.2442, 48.0813, 123.2455, 48.0799),
{label: 'Dadou'});
//将三种作物感兴趣区合并
var cropRegions = new ee.FeatureCollection([gaoliang,yumi,dadou]);
//筛选s2数据
var s2= ee.ImageCollection('COPERNICUS/S2')
.filterDate('2018-01-01', '2019-01-01')
.filterBounds(cropRegions);
//计算每副影像的NDVI并制作数据集
var ndvi = s2.map(function(image) {
return image.select().addBands(image.normalizedDifference(['B8', 'B4']).select([0], ['NDVI']));
});
print(ndvi)
//渲染NDVI显示颜色
var vis = {min: -0.2, max: 1, palette: [
'FFFFFF', 'CE7E45', 'FCD163', '66A000', '207401',
'056201', '004C00', '023B01', '012E01', '011301'
]};
Map.addLayer(ndvi, vis, 'NDVI');

Map.addLayer(cropRegions, {color: COLOR.GAOLIANG},'ROI');
// Map.addLayer(gaoliang, {color: COLOR.GAOLIANG});
// Map.addLayer(yumi, {color: COLOR.YUMI});
// Map.addLayer(dadou, {color: COLOR.DADOU});

//定义图表及样式
var ndviTimeSeries = ui.Chart.image.seriesByRegion({
imageCollection: ndvi,
regions: cropRegions,
reducer: ee.Reducer.mean(),
band: 'NDVI',
scale: 10,
xProperty: 'system:time_start',
seriesProperty: 'label'
});
ndviTimeSeries.setChartType('ScatterChart');
ndviTimeSeries.setOptions({
title: 'Sentinel-2数据作物时间序列NDVI变化',
vAxis: {
title: 'NDVI'
},
lineWidth: 1,
pointSize: 4,
series: {
0: {color: COLOR.GAOLIANG},
1: {color: COLOR.YUMI},
2: {color: COLOR.DADOU}
}
});
print(ndviTimeSeries);