How can I solve this question?

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Example 12.1 Nonlinear Model:

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Eq. 12.19& Eq. 12.20:

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Eq. 12.22& Eq. 12.23:

[KSSV]

What have you attempted?

[Alice Zurock]

clc; clear; close all; format compact; format long eng;

rng('default');

% true signal curve
x = (0:.1e-4:2).'; 
y = .2 * ones(length(x),1) - x + .9 * x.^2 + .7 * x.^3 - .2 * x.^5; 

% plot the true curve
%figure; plot(x1,y1,'b'); 

% training samples (20 or 500)
N = 20; 

% sample interval [a b]
a = 0; b = 2; 

% generate samples
x1 = (a : b/N : b - b/N).';

% noise generation 
sigma_n = .05;
n = sqrt(sigma_n) .* randn(N,1); 

% use the true theta 
theta_true = [.2; -1; .9; .7; -.2]; 

% or a random one
theta_dstrbd = [-0.004; -10.54; 0.465; 0.087; -.093];
l = length(theta_true); 

% compute the measurement matrix
Phi = [ones(N,1) x1 x1.^2 x1.^3 x1.^5];