三次样条插值

Halcom

1. n=2;
   
2. a = polyfit(y,x,2);
   
3. a'
   
4. 
   
5. x1 = a(1).*y.*y + a(2)*y + a(3);
   
6. 
   
7. figure(1)
   
8. plot(y, x, 'b.')
   
9. hold on
   
10. plot(y, x1,'r.')
    
11. hold off;
    
12. 
    
13. %%
    
14. A = [534.0        28965.7        1.60425e+006
    
15. 28965.7        1.60425e+006        9.02824e+007
    
16. 1.60425e+006        9.02824e+007        5.14776e+009];
    
17. B = [1840.57
    
18. 99683.1
    
19. 5.50671e+006];
    
20. a = inv(A)*B
    
21. 
    
22. A1 = [length(y), sum(y), sum(y.^2);
    
23.     sum(y), sum(y.^2), sum(y.^3);
    
24.     sum(y.^2), sum(y.^3), sum(y.^4);];
    
25. B1 = [sum(x); sum(y.*x); sum(y.*y.*x)];
    
26. a = inv(A1)*B1
    
27. 
    
28. x1 = a(3).*y.*y + a(2)*y + a(1);
    
29. 
    
30. figure(2)
    
31. plot(y, x, 'b.')
    
32. hold on
    
33. plot(y, x1,'r.')
    
34. hold off;
    
35. 
    

复制代码