function yi = intrpf(xi,x,y) % Function to interpolate between data points % using Lagrange polynomial (quadratic) % Inputs % x Vector of x coordinates of data points (3 values) % y Vector of y coordinates of data points (3 values) % xi The x value where interpolation is computed % Output % yi The interpolation polynomial evaluated at xi %* Calculate yi = p(xi) using Lagrange polynomial yi = (xi-x(2))*(xi-x(3))/((x(1)-x(2))*(x(1)-x(3)))*y(1) ... + (xi-x(1))*(xi-x(3))/((x(2)-x(1))*(x(2)-x(3)))*y(2) ... + (xi-x(1))*(xi-x(2))/((x(3)-x(1))*(x(3)-x(2)))*y(3); return;