function v=lagrangeint(x,y,u)

tic

n=length(x);
v=zeros(size(u));

for k=1:n
    w=ones(size(u));
    for j=[1:k-1 k+1:n]
        w=(u-x(j))./(x(k)-x(j)).*w;
    end
    v=v+w*y(k);
end
    
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