Update app.py

app.py

@@ -243,14 +243,45 @@ def create_injuries_fatalities_chart(crash_data):
     
     return line_chart
 
+    def create_crash_trend_chart(df, weather=None):
+    """
+    Creates a line graph showing crash trends over time, optionally filtered by weather condition.
+    """
+    # Filter by weather condition if provided
+    if weather and weather != 'All Conditions':
+        df = df[df['Weather'] == weather]
+    
+    # Group data by year and count unique Incident IDs
+    trend_data = df.groupby('Year')['Incidentid'].nunique().reset_index()
+    trend_data.columns = ['Year', 'Crash Count']
+    
+    # Create line graph
+    fig = px.line(
+        trend_data,
+        x='Year',
+        y='Crash Count',
+        title=f'Crash Trend Over Time ({weather})',
+        labels={'Year': 'Year', 'Crash Count': 'Number of Unique Crashes'},
+        markers=True,
+        height=600
+    )
+    
+    fig.update_traces(line=dict(width=2), marker=dict(size=8))
+    fig.update_layout(legend_title_text='Trend')
+    
+    return fig
+
 def main():
     st.title('Traffic Crash Analysis')
     
     # Load data
     df = load_and_preprocess_data('1.08_Crash_Data_Report_(detail).csv')
+
+    if 'Weather' not in df.columns:
+        df['Weather'] = 'Unknown'
     
     # Create tabs for different visualizations
-    tab1, tab2 = st.tabs(["Crash Statistics", "Crash Map"])
+    tab1, tab2, tab3 = st.tabs(["Crash Statistics", "Crash Map", "Crash Trend"])
     
     with tab1:
         # Age group selection
@@ -299,7 +330,17 @@ def main():
                 key=f"map_{selected_year}",
                 returned_objects=["null_drawing"]
             )
-
+            
+    with tab3:
+        # Weather condition filter
+        weather = ['All Conditions'] + sorted(df['Weather'].unique())
+        selected_weather = st.selectbox('Select Weather Condition:', weather)
+        
+        # Create and display line graph
+        st.markdown("### Crash Trend Over Time")
+        trend_fig = create_crash_trend_chart(df, selected_weather)
+        st.plotly_chart(trend_fig, use_container_width=True)
+        
     # Create 5th Visualization: Injuries and fatalities chart
     injuries_fatalities_chart = create_injuries_fatalities_chart(df)
     st.altair_chart(injuries_fatalities_chart, use_container_width=True)