將
function yy=Lagrange(x,y,xi)
m=length(x);
n=length(y);
if m ~= n , error('向量x與y的長度必須壹致'); end;
s=0;
for i=1 : n
z=ones(1,length(xi));
for j=1 : n
if j ~= i
z=z.*(xi-x(j))./(x(i)-x(j));
end
end
s=s+z*y(i);
end
yy=s;
保存為M文件。(文件→新建→M文件)
第二步
將
x=[0.5610,0.56280,0.56401,0.56521];
y=[0.82741,0.82659,0.82577,0.82495];
xi=[0.5625,0.5635,0.5645];
yi=Lagrange(x,y,xi)
粘貼至(命令窗口)。