newtintpoleval.m

Interpolation routines in matlab

%
% Evaluate Newton's interpolating polynomial at
% given points.
%
% function [p] = NewtIntPolEval( x, a, z )
%
% input:
%        x:     vector containing the 
%               interpolation points
%        a:     vector of coefficients of Newton's 
%               interpolating polynomial
%        z:     vector of points at which Newton's 
%               interpolating polynomial has to be
%               evaluated
%
% output:
%        p:     vector of values of Newton's 
%               interpolating polynomial
%
%

function [p] = NewtIntPolEval( x, a, z );


n = size(x(:),1);


if size(a(:),1) ~= n 
   error(' NewtIntPolEval: Dimension of a must be equal to dimension of x')
end

p = a(n) * ones(size(z));
for i = n-1:-1:1
    p = p .* ( z - x(i) * ones(size(z)) ) + a(i);
end