divdifftable.m

数值方法和MATLAB实现与应用.zip

function D = divDiffTable(x,y)
% divdiffTable  Construct a table of divided-difference coefficients
%
% Synopsis:   D = divDiffTable(x,y)
%
% Input:      x,y = vectors containing the tabulated y = f(x) data
%
% Output:     D = matrix containing divided-difference coefficients in
%                 its lower triangle.  Diagonal entries are coefficients
%                 of the Newton polynomial
n = length(y);
if length(x)~=n,   error('x and y are not compatible');   end

D = zeros(n,n);
D(:,1) = y(:);    %  First column is zeroth order difference, f[x_i] = y_i
for j=2:n
  for i=j:n
    D(i,j) = (D(i,j-1)-D(i-1,j-1))/(x(i)-x(i-j+1));
  end
end