update app.py

app.py

@@ -138,6 +138,41 @@ if parameters_changed():
         'end_date_str': end_date_str
     }
 
+# Function to perform index calculations
+def calculate_ndvi(image, geometry):
+    ndvi = image.normalizedDifference(['B8', 'B4']).rename('NDVI')
+    result = ndvi.reduceRegion(
+        reducer=ee.Reducer.mean(),
+        geometry=geometry,
+        scale=30
+    )
+    return result.get('NDVI')
+
+def calculate_ndwi(image, geometry):
+    ndwi = image.normalizedDifference(['B3', 'B8']).rename('NDWI')
+    result = ndwi.reduceRegion(
+        reducer=ee.Reducer.mean(),
+        geometry=geometry,
+        scale=30
+    )
+    return result.get('NDWI')
+
+def calculate_avg_no2_sentinel5p(image, geometry):
+    no2 = image.select('NO2').reduceRegion(
+        reducer=ee.Reducer.mean(),
+        geometry=geometry,
+        scale=1000
+    ).get('NO2')
+    return no2
+
+def calculate_custom_formula(image, geometry, formula):
+    result = image.expression(formula).rename('Custom Index').reduceRegion(
+        reducer=ee.Reducer.mean(),
+        geometry=geometry,
+        scale=30
+    )
+    return result.get('Custom Index')
+
 # Function to calculate the frequency-specific aggregation
 def aggregate_by_frequency(results, frequency):
     # Create an empty list to store the aggregated results