Lab 9 Interactive: Dynamical Systems, Markov Chains, and Perron--Frobenius Theory

Explore repeated multiplication $x_{k+1}=Ax_k$, stationary distributions, convergence, damping, and population growth.

1. Two-state Markov chain

Use a column-stochastic matrix $A=\begin{bmatrix}a&b\\1-a&1-b\end{bmatrix}$.

2. Iteration plot

The plot shows the first component of $x_k$ over time. Convergence appears as flattening.

3. PageRank damping

For a three-page web, form $G=\alpha P+(1-\alpha)\frac{1}{3}\mathbf 1\mathbf 1^T$.

4. Web graph picture

5. Leslie population model

Use $L=\begin{bmatrix}f_1&f_2\\s_1&0\end{bmatrix}$.

6. Population plot

7. Independent-study tasks with answers

Task A. Use $A=\begin{bmatrix}0.9&0.2\\0.1&0.8\end{bmatrix}$. Find the stationary distribution.
Answer: $\pi=(2/3,1/3)^T$.
Task B. Use $A=\begin{bmatrix}0&1\\1&0\end{bmatrix}$. Explain the long-term behavior.
Answer: The state alternates, so it does not converge from $x_0=(1,0)^T$.
Task C. Increase the PageRank damping teleportation term by lowering $\alpha$. What happens?
Answer: The ranking becomes closer to uniform because random jumps become more important.
Task D. In the Leslie model, what does the dominant eigenvalue represent?
Answer: The asymptotic growth factor per time step.

8. Workspace