// Get a feature collection of Thailand
var c = ee.FeatureCollection('USDOS/LSIB_SIMPLE/2017').filter(ee.Filter.eq('country_na', 'Thailand'));
//             Map.addLayer(c);      
// ใช้ข้อมูลSentinel-2 
var image = ee.ImageCollection('COPERNICUS/S2')
//เปลี่ยนช่วงเวลาที่สนใจ
.filterDate('2021-12-01', '2021-12-31')
//filter according to drawn boundary
.filterBounds(c);
// Function to mask cloud from built-in quality band
// information on cloud
var maskcloud1 = function(image) {
var QA60 = image.select(['QA60']);
return image.updateMask(QA60.lt(1));
};
// Function to calculate and add an NDVI band
var addNDVI = function(image) {
return image.addBands(image.normalizedDifference(['B8', 'B4']));
};
// Add NDVI band to image collection
var S2 = image.map(addNDVI);

// Sentinel-2 Band
var B = S2.median().select(['B2']);
var G = S2.median().select(['B3']);
var R = S2.median().select(['B4']);
var NIR = S2.median().select(['B8']);
var B11 = S2.median().select(['B11']);
var B12 = S2.median().select(['B12']);

// Extract NDVI band and create NDVI median composite image
var NDVI = S2.median().normalizedDifference(['B8', 'B4']);
var NDWI = S2.median().normalizedDifference(['B3', 'B8']);
var RI = S2.median().expression(
  "(10**5)*((RED**2) / (BLUE * (RED**3)))",
    {'BLUE': B,
    'RED': R,
    });
var SI = S2.median().expression(
  "(RED-BLUE) / RED ",
    {'BLUE': B,
    'RED': R,
    });
var FI = S2.median().expression(
  "((2*RED)-GREEN-BLUE) / (GREEN-BLUE) ",
    {'BLUE': B,
     'GREEN': G,
    'RED': R,
    });

var SCI = S2.median().normalizedDifference(['B4', 'B3']);
var BI = S2.median().expression(
  "sqrt((GREEN**2)+(RED**2)+(NIR**2)) / 10**4 ",
    {'NIR': NIR,
     'GREEN': G,
    'RED': R,
    }); 
var NDTI = S2.median().normalizedDifference(['B11', 'B12']);
var STI = B11.divide(B12);
// Create palettes for display 
var pal = [
    '040274', '040281', '0502a3', '0502b8', '0502ce', '0502e6',
    '0602ff', '235cb1', '307ef3', '269db1', '30c8e2', '32d3ef',
    '3be285', '3ff38f', '86e26f', '3ae237', 'b5e22e', 'd6e21f',
    'fff705', 'ffd611', 'ffb613', 'ff8b13', 'ff6e08', 'ff500d',
    'ff0000', 'de0101', 'c21301', 'a71001', '911003'];

// Set map center 
Map.centerObject(c, 6);

//Display NDVI results on map
Map.addLayer(NDVI.clip(c), {min:0.1, max:0.5, palette: pal}, 'NDVI');
Map.addLayer(NDWI.clip(c), {min:-1, max:0.5, palette: pal}, 'NDWI');
Map.addLayer(RI.clip(c), {min:0, max:0.5, palette: pal}, 'Redness Index');
Map.addLayer(SI.clip(c), {min:-0.5, max:0.5, palette: pal}, 'Saturate Index');
Map.addLayer(FI.clip(c), {min:0, max:10, palette: pal}, 'Form Index');
Map.addLayer(SCI.clip(c), {min:-0.5, max:0.5, palette: pal}, 'Soil Color Index');
Map.addLayer(BI.clip(c), {min:0, max:0.5, palette: pal}, 'Brightness Index');
Map.addLayer(NDTI.clip(c), {min:-0.2, max:0.5, palette: pal}, 'Normalized Difference Tillage Index');
Map.addLayer(STI.clip(c), {min:1, max:2, palette: pal}, 'Soil Tillage Index');

//Export data to your google drive
//Export the NDVI, specifying scale and region.
Export.image.toDrive({
  image: NDVI,
  description: 'NDVI',
 scale: 10,
 region: c,
 maxPixels: 1e13,
});

//Export the NDWI, specifying scale and region.
Export.image.toDrive({
  image: NDWI,
  description: 'NDWI',
 scale: 10,
 region: c,
 maxPixels: 1e13,
});
//Export the RI, specifying scale and region.
Export.image.toDrive({
  image: RI,
  description: 'RI',
 scale: 20,
 region: c,
 maxPixels: 1e13,
});
//Export the SI, specifying scale and region.
Export.image.toDrive({
  image: SI,
  description: 'SI',
 scale: 10,
 region: c,
 maxPixels: 1e13,
});

//Export the FI, specifying scale and region.
Export.image.toDrive({
  image: FI,
  description: 'FI',
 scale: 10,
 region: c,
 maxPixels: 1e13,
});

//Export the SCI, specifying scale and region.
Export.image.toDrive({
  image: SCI,
  description: 'SCI',
 scale: 10,
 region: c,
 maxPixels: 1e13,
});
//Export the BI, specifying scale and region.
Export.image.toDrive({
  image: BI,
  description: 'BI',
 scale: 10,
 region: c,
 maxPixels: 1e13,
});

//Export the NDTI, specifying scale and region.
Export.image.toDrive({
  image: NDTI,
  description: 'NDTI',
 scale: 20,
 region: c,
 maxPixels: 1e13,
});

//Export the STI, specifying scale and region.
Export.image.toDrive({
  image: STI,
  description: 'STI',
 scale: 20,
 region: c,
 maxPixels: 1e13,
});