Are these polyfit curves correct?

This is what I have to do:

Create an m-file that uses the polyfit, linspace, polyval and plot functions to create a plot of the data listed below along with a least-squares line, a third-degree polynomial and a five-degree polynomial fit. Plot the curves with 100 data points (linspace default) to produce smooth fit curves.

x = [-8, -6, -4, -2, -1, 0, 1, 2, 4, 6, 8]
y = [0.1, 0.2, 0.5, 0.7, 2.2, 3.8, 5.5, 3.6, 2.8, 4.0, 3.5]

This is what I have so far.

x = linspace(-8,8);

y = linspace(0.1,3.5);

p = polyfit(x,y,3);

x2 = 0:0.1:3.1;

y2 = polyval(p,x2);

v = polyfit(x,y,5);

c = polyval(v,x2);

subplot(2,1,1)

plot(x,y,x2,y2)

legend('x,y,polyfit')

xlabel('x')

ylabel('y')

subplot(2,1,2)

plot(x,y,x2,c)

legend('x,y,polyfit')

xlabel('x')

ylabel('y')

[Walter Roberson]

Looks plausible.

Answer 1

[madhan ravi]

Codes are correct

%one remark

%x2=-8:0.1:8

%because the start and endpoint should be similar to x.

plot(x,y,'ob'x2,y2,'')

%use line markers to distinguish between them :)