# Given a set of date point x and y, estimate three polynomial functions (2nd degree, 3rd degree, 4th degree) that will best fit the data.

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Given a set of date point x and y, estimate three polynomial functions (2nd degree, 3rd degree, 4th degree) that will best fit the data. Compute new set of y data from the three functions and determine which of the three functions will give the least norm difference.

This is what I've came up with, but still not sure if it really satisfy the problem.

x=[0.9 1.5 3 4 6 8 9.5];

y=[0.9 1.5 2.5 5.1 4.5 4.9 6.3];

p=polyfit(x,y,3)

xp=0.9:0.1:9.5;

yp=polyval(p,xp);

plot(x,y,'o',xp,yp)

xlabel('x'); ylabel('y')

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### Answers (1)

Walter Roberson
on 27 Nov 2021

##### 2 Comments

Walter Roberson
on 27 Nov 2021

x = [0.9 1.5 3 4 6 8 9.5];

y = [0.9 1.5 2.5 5.1 4.5 4.9 6.3];

p = polyfit(x,y,2);

l = polyfit(x,y,3);

t = polyfit(x,y,4);

xp = 0.9:0.1:9.5;

yp1 = polyval(p,xp);

yp2 = polyval(l,xp);

yp3 = polyval(t,xp);

xlabel('x');

ylabel('y');

plot(x,y,'o',xp,yp1,xp,yp2,xp,yp3)

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