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heyy
Posted:
May 9, 2013 12:23 PM


I am writing a MATLAB function for cubic interpolation, without using MATLAB's inbuit spline fuction.
How do you use MATLAB's / operator to solve the system of linear equation. Do you know anyway to do this simple.
Thank You.
function [s0,s1,s2,s3]=cubic_spline(x,y)
if any(size(x) ~= size(y))  size(x,2) ~= 1 error('inputs x and y must be column vectors of equal length'); end
n = length(x)
h = x(2:n)  x(1:n1); d = (y(2:n)  y(1:n1))./h;
lower = h(1:end1); main = 2*(h(1:end1) + h(2:end)); upper = h(2:end);
T = spdiags([lower main upper], [1 0 1], n2, n2); rhs = 6*(d(2:end)d(1:end1));
m = T\rhs;
% Use natural boundary conditions where second derivative % is zero at the endpoints
m = [ 0; m; 0];
s0 = y; s1 = d  h.*(2*m(1:end1) + m(2:end))/6; s2 = m/2; s3 =(m(2:end)m(1:end1))./(6*h);



