Matlab piecelin

function v = piecelin(x,y,u)%PIECELIN  Piecewise linear interpolation.%  v = piecelin(x,y,u) finds the piecewise linear L(x)%  with L(x(j)) = y(j) and returns v(k) = L(u(k)).%  First divided difference   delta = diff(y)./diff(x);%  Find subinterval indices k so that x(k) <= u < x(k+1)   n = length(x);   k = ones(size(u));   for j = 2:n-1      k(x(j) <= u) = j;   end%  Evaluate interpolant   s = u - x(k);   v = y(k) + s.*delta(k);