update app.py

app.py

@@ -76,8 +76,20 @@ elif index_choice.lower() == 'ndwi':
 elif index_choice.lower() == 'average no₂':
     st.write("Formula for Average NO₂: Average NO₂ = Mean(NO2 band)")
 elif index_choice.lower() == 'custom formula':
-    custom_formula = st.text_input("Enter Custom Formula (e.g., 'B5 - B4 / B5 + B4')")
-    st.write(f"Custom Formula: {custom_formula}")  # Display the custom formula after the user inputs it
+    # Get the bands for the selected dataset category
+    bands = data[main_selection]["bands"]
+    # Allow the user to select up to 3 bands
+    band_selection = st.multiselect("Select up to 3 bands for custom calculation", bands, max_selections=3)
+    
+    # Show the selected bands in the custom formula input
+    if len(band_selection) > 0:
+        st.write("You selected the following bands:")
+        st.write(band_selection)
+    
+    # Allow the user to enter a custom formula with the selected bands
+    if band_selection:
+        custom_formula = st.text_input("Enter Custom Formula (e.g., 'B5 - B4 / B5 + B4')")
+        st.write(f"Custom Formula: {custom_formula}")  # Display the custom formula after the user inputs it
 
 # Function to check if the polygon geometry is valid and convert it to the correct format
 def convert_to_ee_geometry(geometry):
@@ -153,33 +165,11 @@ if parameters_changed():
     }
 
 # 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):
+def calculate_custom_formula(image, geometry, formula, band_selection):
+    # Replace band names in the formula with actual band values
+    for i, band in enumerate(band_selection, 1):
+        formula = formula.replace(f'B{i}', band)
+    # Apply the formula using Earth Engine expression
     result = image.expression(formula).rename('Custom Index').reduceRegion(
         reducer=ee.Reducer.mean(),
         geometry=geometry,
@@ -271,17 +261,8 @@ if file_upload:
 
                 # Perform the calculation based on user selection
                 result = None
-                if index_choice.lower() == 'ndvi':
-                    result = calculate_ndvi(image, roi)
-                elif index_choice.lower() == 'ndwi':
-                    result = calculate_ndwi(image, roi)
-                elif index_choice.lower() == 'average no₂':
-                    if 'NO2' in image.bandNames().getInfo():
-                        result = calculate_avg_no2_sentinel5p(image, roi)
-                    else:
-                        st.warning(f"No NO2 band found for {location_name}. Please use Sentinel-5P for NO₂ data.")
-                elif index_choice.lower() == 'custom formula' and custom_formula:
-                    result = calculate_custom_formula(image, roi, custom_formula)
+                if index_choice.lower() == 'custom formula' and custom_formula:
+                    result = calculate_custom_formula(image, roi, custom_formula, band_selection)
 
                 if result is not None:
                     # Only store the numeric value (not the dictionary structure)
@@ -348,17 +329,8 @@ if file_upload:
 
                 # Perform the calculation based on user selection
                 result = None
-                if index_choice.lower() == 'ndvi':
-                    result = calculate_ndvi(image, roi)
-                elif index_choice.lower() == 'ndwi':
-                    result = calculate_ndwi(image, roi)
-                elif index_choice.lower() == 'average no₂':
-                    if 'NO2' in image.bandNames().getInfo():
-                        result = calculate_avg_no2_sentinel5p(image, roi)
-                    else:
-                        st.warning(f"No NO2 band found for {location_name}. Please use Sentinel-5P for NO₂ data.")
-                elif index_choice.lower() == 'custom formula' and custom_formula:
-                    result = calculate_custom_formula(image, roi, custom_formula)
+                if index_choice.lower() == 'custom formula' and custom_formula:
+                    result = calculate_custom_formula(image, roi, custom_formula, band_selection)
 
                 if result is not None:
                     # Only store the numeric value (not the dictionary structure)
@@ -395,4 +367,3 @@ if st.session_state.results:
         file_name=filename,
         mime='text/csv'
     )
-