Update app.py

app.py

@@ -243,6 +243,30 @@ def create_injuries_fatalities_chart(crash_data, unit_type):
     
     return line_chart
 
+def create_crash_trend_chart(df, weather=None):
+    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')