sanciyangtiao.m

一些matlab程序

function s=csfit(x,y,dx0,dx1)
clear all
  x=[0 1 2 3];
 y=[0 0.5 2.0 1.5];
 dx0=0.2;dxn=-1;
 n=length(x)-1;
 h=diff(x) ;
 d=diff(y)./h;
 a=h(2:n-1);
 b=2*(h(1:n-1)+h(2:n));
 c=h(2:n);
 u=6*diff(d);
 b(1)=b(1)-h(1)/2;
 u(1)=u(1)-3*(d(1)-dx0);
 b(n-1)= b(n-1)-h(n)/2;
  u(n-1)=u(n-1)-3*(dxn-d(n));
  for k=2:n-1
      temp=a(k-1)/b(k-1);
      b(k)=b(k)-temp*c(k-1);
      u(k)=u(k)-eye(k-1);
  end
  m(n)=u(n-1)/b(n-1);
  for k=n-2:-1:1
      m(k+1)=(u(k)-c(k)*m(k+2))/b(k);
  end
  m(1)=3*(d(1)-dx0)/h(1)-m(2)/2;
  m(n+1)=3*(dxn-d(n))/h(n)-m(n)/2;
  for k=0:n-1
      s(k+1:1)=(m(k+2)-m(k+1))/(6*h(k+1))
       s(k+1:2)=m(k+1)/2
       s(k+1:3)=d(k+1)-h(k+1)*(2*m(k+1)+m(k+2))/6
       s(k+1:4)=y(k+1)
   end