feat(5-min-viz): add checks to visualization

ensure that the required parameters are set before proceeding
with the visualization

Author: lalver1

pems_streamlit/src/pems_streamlit/apps/stations/app_stations.py

@@ -75,13 +75,24 @@ def main():
     station_data_button = st.button("Load Station Data", type="primary")
 
     if station_data_button:
-        df_station_data = load_station_data(station)
-        filtered_df = df_station_data[
-            (df_station_data["SAMPLE_TIMESTAMP"].dt.day.isin(days)) & (df_station_data["LANE"].isin(lane))
-        ]
-        st.dataframe(df_station_data, use_container_width=True)
-        filtered_df_sorted = filtered_df.sort_values(by="SAMPLE_TIMESTAMP")
-        plot_5_min_traffic_data(filtered_df_sorted, quantity, lane)
+        error_messages = []
+        if len(quantity) == 0 or len(quantity) > 2:
+            error_messages.append("- Please select one or two quantities to proceed.")
+        if not lane:
+            error_messages.append("- Please select at least one lane to proceed.")
+        if not days:
+            error_messages.append("- Please select at least one day to proceed.")
+        if error_messages:
+            full_error_message = "\n".join(error_messages)
+            st.error(full_error_message)
+        else:
+            df_station_data = load_station_data(station)
+            filtered_df = df_station_data[
+                (df_station_data["SAMPLE_TIMESTAMP"].dt.day.isin(days)) & (df_station_data["LANE"].isin(lane))
+            ]
+            st.dataframe(df_station_data, use_container_width=True)
+            filtered_df_sorted = filtered_df.sort_values(by="SAMPLE_TIMESTAMP")
+            plot_5_min_traffic_data(filtered_df_sorted, quantity, lane)
 
 
 if __name__ == "__main__":