lagranp.m

来自「辛普森方法」· M 代码 · 共 15 行

function [l,L] = lagranp(x,y)
%Input : x = [x0 x1 ... xN], y = [y0 y1 ... yN]
%Output: l = Lagrange polynomial coefficients of degree N
%        L = Lagrange coefficient polynomial

N = length(x)-1; %the degree of polynomial
l = 0;
for m = 1:N + 1
  P = 1;
  for k = 1:N + 1
    if k ~= m, P = conv(P,[1 -x(k)])/(x(m)-x(k)); end
  end
  L(m,:) = P; %Lagrange coefficient polynomial
  l = l + y(m)*P; %Lagrange polynomial
end