拉格朗日插值.txt

方便初学者！插值与拟合的matlab实现！ 可方便同学做课设！

function Ys=langr(X,Y,Xs)
%拉格朗日插值
n=length(X);
nl=length(Xs);



for i=1:nl
    x=Xs(i);
    s=0;
    for j=1:n
        p=1;
        for k=1:n
            if k~=j
                p=p*(x-X(k))/(X(j)-X(k));
            end 
        end
        s=s+p*Y(j);       
    end 
    Ys(i)=s;
end


function y=lagrange(x0,y0,x);
n=length(x0);m=length(x);
for i=1:m
  z=x(i);
  s=0.0;
  for k=1:n
      p=1.0;
      for j=1:n
          if j~=k
            p=p*(z-x0(j))/(x0(k)-x0(j));
          end
      end
      s=p*y0(k)+s;
    end
    y(i)=s;
end