Practice problem on Linear & Quadratic Fit | MATLAB

Problem Statement:
Consider 6 points in a two-dimensional space:
(1, 2), (2, 3), (1,−1), (−1, 3), (1,−2), (0,−1)
Build a MATLAB figure in which the points are represented with their linear and quadratic regression functions.

Prerequisite: Polynomial Regression in MATLAB

%Code:

clc

clear all

close all

x=[1 2 1 -1 1 0];

y=[2 3 -1 3 -2 -1];

a=1;

coeff=polyfit(x,y,a);

t=min(x):0.01:max(x);

c=0;

temp=a;

z=[];

for i=1:length(t)

t1=t(i);

for j=1:length(coeff)

c=c+coeff(j)*(t1^temp);

temp=temp-1;

end

temp=a;

z=[z c];

c=0;

end

plot(t,z,'--');

hold on;

plot(x,y,'o');

a=2;

coeff=polyfit(x,y,a);

t=min(x):0.01:max(x);

c=0;

temp=a;

z=[];

for i=1:length(t)

t1=t(i);

for j=1:length(coeff)

c=c+coeff(j)*(t1^temp);

temp=temp-1;

end

temp=a;

z=[z c];

c=0;

end

plot(t,z);

hold off;