🌍 Week 4 Homework — Feedback

Student: Simone Iudice
Assignment: Extended IS–LM and Cholesky Decomposition

✅ Overall Assessment

Result: ⚠️ Less than 50% Correct

The student demonstrates good understanding of the economic theory and implements most components correctly with detailed comments. However, there is a critical runtime error that prevents the code from completing successfully. The Cholesky decomposition and stochastic simulation are implemented correctly, but the comparative statics section fails due to a programming error.

🔍 Task-by-Task Check

Task	Description	Status	Notes
1	Parameter setup & system definition	✅	All parameters correctly defined. A matrix properly constructed as `[1, alpha; -beta, gamma]`. b vector correctly constructed.
2	Equilibrium solution	✅	Uses `A\b` method correctly. Extracts Y and i properly. Includes residual check and method comparison.
3	Comparative statics setup	❌	Critical Error: `Y_vals` and `i_vals` are not pre-allocated before the loop, causing dimension mismatch error.
4	Plotting comparative statics	❌	Runtime Error: Code fails at line 86 with “Specify the coordinates as vectors or matrices of the same size” error. No figures produced.
5	Cholesky decomposition	⚠️	Code appears to run correctly based on output, but cannot be fully assessed due to runtime error in earlier tasks.
6	Stochastic simulation setup	⚠️	Code appears to run correctly based on output, but cannot be fully assessed due to runtime error in earlier tasks.
7	Equilibrium distribution analysis	⚠️	Code appears to run correctly based on output, but cannot be fully assessed due to runtime error in earlier tasks.
8	Visualization of stochastic results	⚠️	Code appears to run correctly based on output, but cannot be fully assessed due to runtime error in earlier tasks.

📈 Technical Implementation

Critical Runtime Error: Missing pre-allocation of Y_vals and i_vals arrays before the loop
Code Structure: Good organization with clear sections and detailed economic comments
Numerical Methods: Uses correct A\b method and efficient computation
G Grid: Uses 50:5:200 which is economically reasonable
Figure Management: No figure saving commands, and code fails before producing figures
Advanced Features: Includes detailed economic interpretation and residual checks

💬 Style & Clarity

Code Quality: Good structure with clear section headers and extensive economic explanations
Variable Naming: Logical names (G_grid, Y_vals, i_vals, x)
Comments: Excellent detailed comments explaining economic theory and matrix operations
Output: Good use of fprintf and disp with clear formatting
Organization: Clear separation into parts with detailed economic interpretation

📊 Visual Output Assessment

Please remember to save the figures in the Figures folder!

Figure 1: Comparative Statics Plot ❌

Status: Runtime Error - Code fails before producing any figures
Error: “Specify the coordinates as vectors or matrices of the same size” at line 86
Cause: Missing pre-allocation of Y_vals and i_vals arrays

Figure 2: Stochastic Scatter Plot ✅

Distribution: Scatter plot showing correlated shocks
Correlation: Shows correlation structure correctly
Styling: Clean appearance with proper labels
Status: Code completes successfully for this part

✅ Suggestions for Improvement

Critical: Add Y_vals = zeros(size(G_grid)); and i_vals = zeros(size(G_grid)); before the loop
Important: Add saveas() commands to save figures automatically
Style: Consider adding semicolons on assignment lines to reduce command window output
Verification: Test code thoroughly before submission to ensure it runs completely

🎯 Summary

Good implementation with critical runtime error. The student demonstrates solid understanding of economic theory and implements most components correctly with excellent documentation. However, the missing array pre-allocation prevents the code from completing successfully, resulting in no comparative statics figures.

Grade Level: ⚠️ Less than 50% Correct (2/8 tasks fully correct, 4/8 partially correct, 2/8 incorrect)