function xia3241(x,y,a,b,s)
plot(x,y,'or')
hold on

n=length(x);
A=ones(1,n);
for i=1:s;
    A=[A;x.^i];
end
xia324=inline(inv(A*A')*A*y');
m=length(xx);
for j=1:m;
    yy1(j)=xx(m-j+1);
end
for i=1:n;
    r(i)=y(i)-polyval(yy1,x(i));
end

xx=linspace(a,b,100);
yy=xia324(x,y,xx,s);
plot(xx,yy,'b')
hold off

function [yy1,r]=xia3242(x,y,s)
n=length(x);
A=ones(1,n);
for i=1:s;
    A=[A;x.^i];
end
xx=inv(A*A')*A*y';
m=length(xx);
for j=1:m;
    yy1(j)=xx(m-j+1);
end
for i=1:n;
    r(i)=y(i)-polyval(yy1,x(i));
end