function a = Coef(n, x, y)
% This procedure requires:
% x = horizontal array of x values
% y = horizontal array of y values
% n = degree of interpolation polynomial
% [This means that there must be (n + 1) elements in
% x and y.]
%
% My example was:
% x = [1 2 4 5]
% y = [3 4 0 -5]
% a = coef(3, x, y)
% [Type the above into the Command Window!]
% MATLAB will copy the coefficients into the horizontal
% array "a".
%
% First, copy y into a.
a = y;
% Now calculate the coefficients.
% We only run the j loop a total of n times.  (Each loop is
% successively shorter.)
% The starting and stopping values for i were modifed to
% accomodate positive indices in MATLAB.
for j=1:n
    for i=(n+1):-1:(j+1)
        a(i) = (a(i) - a(i-1))/(x(i) - x(i-j));
    end
end