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# MATLAB (Must be scripted in MATLAB)

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I need a detailed script in order to show this works in MATLAB.

On this page the only problem I need it #26 (the circled problem with the Taylor expansion).

https://brainmass.com/computer-science/matlab/matlab-scripted-matlab-113448

#### Solution Summary

The expert provides MATLAB scripts for functions.

\$2.19

## Matlab for Lorenz equations with Gauss Seidel iteration

Hello

I am taking a numerical methods class and I have limited Matlab skills to be able to complete this problem by myself.

The problem is to linearize the Lorenz equations and then to write a Matlab program without using any built in Matlab solvers such as ODE45, etc. to create the Lorenz butterfly using linearized Lorenz equations with Gauss-Seidel iteration.

I have the linearized Lorenz equations, constants, stopping criteria and initial conditions here:

stopping criteria: 1.e-6
initial conditions: x = 2, y = 2, z = 4
sigma = 10, rho = 28, beta = 8/3
delta_t = 1.e-4

linearized lorenz equations:

x^n+1 - x^n = delta_t * sigma*(y^n+1 - x^n+1)
[please rewrite so equation begins x^n+1 = ...]

y^n+1 = (1 + delta_t*x^n+1*(rho - z^n+1)/(1 + delta_t)

z^n+1 = (1 + delta_t * x^n+1 * y^n+1)/(1 + beta * delta_t)

The code MUST only use Gauss-Seidel iteration to run the iterations (no RK2 or other methods). The code may not use any built in Matlab functions or solvers or matrices to store answers. It needs to tell how much CPU time was used (incorporate tic toc?) What was also suggested was to use a file to dump all results to while the iterations run, making the program run faster. With the results of the iterations a 3D plot needs to be plotted to show the Lorenz butterfly (attractor) using delta_t = 1.e-4. Then a second plot needs to be created that shows the x on the vertical axis and t on the horizontal axis plotting both delta_t = 1.e-4 and delta_t = 1.e-5 so you can see how a slight variation in delta_t causes the two lines to depart after a short while

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