polynomial regression of a given function

i am trying to write a function which produces the regression polynomial of degree 2 for a given datapoints (x and f(x) where f is the function to be approximated). this is what i wrote !! the code gives me 0 errors but i can not plot the results for some reasons that i dont know

x=input('Enter the x coordinates');

y=input('Enter the y coordinates');

n=input('Enter the order of the polynomial');

coeff=polyfit(x,y,n);

p = polyfit(x,y,n);

plot p;

Answer 1

[Jon]

You only solved for the coefficients. If you want to compare the original data and the fit you can do something like this, after your code above (I assume the x values are entered in increasing order)

xfit = linspace(x(1),x(end))
yfit = polyval(p,xfit);
plot(x,y,'o',xfit,yfit,'-')

[Anas Gharsa]

Yes that's right!! i intend to enter the x values in increasing order!!! Thank you so much this is so helpful