Code Editor for app.py

import streamlit as st
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

st.title("Actuarial Cashflow Model Analyzer")

# Sidebar inputs
st.sidebar.header("Model Parameters")
initial_investment = st.sidebar.number_input("Initial Investment", min_value=0, value=100000)
interest_rate = st.sidebar.slider("Annual Interest Rate (%)", 0.0, 20.0, 5.0)
years = st.sidebar.slider("Projection Years", 1, 50, 30)
payment_freq = st.sidebar.selectbox("Payment Frequency", ["Annual", "Semi-Annual", "Quarterly", "Monthly"])

# Calculate payment frequency multiplier
freq_multiplier = {
    "Annual": 1,
    "Semi-Annual": 2,
    "Quarterly": 4,
    "Monthly": 12
}[payment_freq]

# Optional cashflow inputs
st.sidebar.header("Additional Cashflows")
regular_contribution = st.sidebar.number_input("Regular Contribution", value=0)
withdrawal_rate = st.sidebar.slider("Annual Withdrawal Rate (%)", 0.0, 20.0, 0.0)

# Calculate time points and cashflows
periods = years * freq_multiplier
time_points = np.arange(0, periods + 1) / freq_multiplier
periodic_rate = (1 + interest_rate/100) ** (1/freq_multiplier) - 1

# Initialize cashflow array
balance = np.zeros(periods + 1)
balance[0] = initial_investment

# Calculate balance over time
for i in range(1, periods + 1):
    # Previous balance with interest
    balance[i] = balance[i-1] * (1 + periodic_rate)
    
    # Add regular contribution
    balance[i] += regular_contribution
    
    # Subtract withdrawals
    withdrawal = balance[i] * (withdrawal_rate/100) / freq_multiplier
    balance[i] -= withdrawal

# Create main display area
st.header("Cashflow Analysis")

# Display chart
fig, ax = plt.subplots(figsize=(10, 6))
ax.plot(time_points, balance, 'b-', label='Account Balance')
ax.fill_between(time_points, 0, balance, alpha=0.2)
ax.set_xlabel('Years')
ax.set_ylabel('Balance')
ax.set_title('Projected Account Balance Over Time')
ax.grid(True)
ax.legend()

st.pyplot(fig)

# Key metrics
final_balance = balance[-1]
total_contributions = initial_investment + regular_contribution * periods
total_interest = final_balance - total_contributions
total_withdrawals = sum(balance * (withdrawal_rate/100) / freq_multiplier)

# Display metrics
col1, col2, col3 = st.columns(3)

with col1:
    st.metric("Final Balance", f"${final_balance:,.2f}")

with col2:
    st.metric("Total Interest Earned", f"${total_interest:,.2f}")

with col3:
    st.metric("Total Withdrawals", f"${total_withdrawals:,.2f}")

# Display detailed data
st.header("Detailed Cashflow Data")
df = pd.DataFrame({
    'Year': time_points,
    'Balance': balance,
    'Interest Earned': balance * periodic_rate,
    'Withdrawal': balance * (withdrawal_rate/100) / freq_multiplier
})

st.dataframe(df.round(2))