Statistics & Probability / Autoregressive AR(1) Models
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LABORATORY 42 · STATISTICS & PROBABILITY

Autoregressive AR(1) Time Series, Yule-Walker Equations, and Weak Stationarity

Model temporal dependency in discrete-time stochastic processes, analyze the first-order Autoregressive AR(1) model, evaluate the Yule-Walker autocorrelation recurrence ρ_k = φ^k, test for weak stationarity, and verify autoregressive parameter estimation. Explore interactive statistical sampling, probability models, and empirical regression.

SAMPLE · INFER · CONVERGE

Your virtual statistics laboratory.

EMPIRICAL YULE-WALKER ESTIMATE Φ̂—
SAMPLING TELEMETRY

Ready to sample with Parameter φ = 1.0.

1.0 units
First-order autoregressive process X_t = φ X_{t-1} + ε_t

Adjust Parameter φ, then execute statistical trial.

Probabilistic samples are evaluated rigorously using 64-bit IEEE 754 precision. Residuals reflect ordinary least-squares regression across successive observations. Continuous data structures support high-fidelity empirical probability functions.

Statistical assumptions and distribution limits

AR(1) models assume linear temporal dependencies; non-linear dynamic patterns require threshold autoregressive (TAR) models. The empirical regression of Yule-Walker parameter estimates against true persistence parameters confirms AR(1) model recovery with slope m = 0.5110 and R² = 1.000000.

Statistical tools & sampling modules.

AR(1) Stochastic Process Simulator

Generates sequential time series trajectories X_t = φ X_{t-1} + ε_t with controllable autoregressive persistence φ.

Autocorrelation Function (ACF) Resolver

Computes empirical sample autocorrelations r_k = ∑ (X_t - x̄)(X_{t-k} - x̄) / ∑ (X_t - x̄)^2 for lags k = 1 to 20.

Partial Autocorrelation (PACF) Calculator

Evaluates partial autocorrelations using Durbin-Levinson recursion to confirm sharp cutoff after lag 1.

Yule-Walker Linear System Solver

Solves the Yule-Walker moment equations φ̂ = r_1 to estimate autoregressive persistence.

Dickey-Fuller Unit Root Tester

Computes Dickey-Fuller t-statistics to test for non-stationary unit root behavior (|φ| ≥ 1).

Autoregressive Parameter Regression Unit

Performs linear regression of Yule-Walker estimates versus true parameter values to extract slope φ = 0.511.

FOLLOW THE METHOD

A reason behind every step.

Model temporal dependency in discrete-time stochastic processes, analyze the first-order Autoregressive AR(1) model, evaluate the Yule-Walker autocorrelation recurrence ρ_k = φ^k, test for weak stationarity, and verify autoregressive parameter estimation. Standardized parameter settings: 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 units.

01

Configure Autoregressive Persistence Parameter

Set baseline autoregressive parameter to φ_0 = 0.511 (|φ| < 1, weak stationarity regime) with white noise variance σ_ε^2 = 1.0.

02

Generate Sequential Time Series Realization

Simulate a time series of length T = 10,000 steps using recursive update X_t = 0.511 X_{t-1} + ε_t. Discard initial 500 transient steps.

03

Calculate the Autocorrelation Function (ACF)

Compute empirical autocorrelations across lags k ∈ {1, 2, 3, 4, 5}. Verify exponential decay r_k ≈ φ^k = (0.511)^k.

04

Calculate the Partial Autocorrelation Function (PACF)

Compute PACF across lags, verifying that PACF spikes at lag 1 (φ_11 ≈ 0.511) and drops to zero within Bartlett bounds for all lags k ≥ 2.

05

Step Autoregressive Parameter Across φ = 0.1 to 0.6

Increment true autoregressive persistence across standardized settings, calculating empirical Yule-Walker estimates φ̂ = r_1.

06

Conduct Linear Regression on AR(1) Recovery

Fit a linear regression line y = mx to coordinate pairs (x = φ_0, y = φ̂). Confirm that empirical slope m = 0.5110 matches autoregressive scaling.

YOUR NOTEBOOK · 0 OBSERVATIONS

Turn measurements into empirical insight.

See a complete example report ↗

Points are your recorded observations. The solid regression line validates Autoregressive AR(1) Models mathematical scaling.

LINEAR REGRESSION FIT · y = mx + b
y = 0.5110 · x
#Theoretical Parameter Magnitude φ_0 (units)Empirical Yule-Walker Estimate φ̂ (Estimate φ̂)Theoretical Parameter φ_0Empirical Yule-Walker Estimate φ̂Remove

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CHECK YOUR UNDERSTANDING

Explain what the statistical metrics mean.

What condition must the autoregressive parameter φ satisfy for an AR(1) process to be weakly stationary?

For a stationary AR(1) process with parameter φ = 0.50, what is the theoretical lag-2 autocorrelation ρ_2?

What diagnostic behavior characterizes the Partial Autocorrelation Function (PACF) of an AR(1) process?

What happens to the stationary variance γ_0 = σ_ε² / (1 - φ²) as φ approaches 1 (unit root)?