% ECE 111 Lecture #4
% Compute the derivative of y(x)

function [dy] = Derivative(x, y)

   npt = length(x)

   dy = 0*x;

   for i=2:npt-1
      dy(i) = ( y(i+1)-y(i-1) ) / (x(i+1)-x(i-1));
      end

   dy(1) = (y(2)-y(1))/(x(2)-x(1));
   dy(npt) = (y(npt)-y(npt-1))/(x(npt)-x(npt-1));
   end