拉格朗日插值法matlab程序

syms t;
if(length(x) == length(y))
n = length(x);
else
disp('x和y的维数不相等！');
return;
end %检错

f = 0.0;
for(i = 1:n)
l = y(i);
for(j = 1:i-1)
l = l*(t-x(j))/(x(i)-x(j));
end;
for(j = i+1:n)
l = l*(t-x(j))/(x(i)-x(j)); %计算拉格朗日基函数
end;

f = f + l; %计算拉格朗日插值函数
simplify(f); %化简

if(i==n)
if(nargin == 3)
f = subs(f,'t',x0); %计算插值点的函数值
else
f = collect(f); %将插值多项式展开
f = vpa(f,6); %将插值多项式的系数化成6位精度的小数
end
end