數(shù)值分析函數(shù)擬合MATLAB代碼

1、第一題MATLAB代碼：%用spline作圖xi=0.2 0.4 0.6 0.8 1.0;yi=0.98 0.92 0.81 0.64 0.38;x=-1:0.01:2;y1=Newton3(xi,yi,x; %源代碼見(jiàn)m文件y2=spline(xi,yi,x;plot(xi,yi,'o',x,y1,'r-',x,y2,'k'%用csape作圖xi=0.2 0.4 0.6 0.8 1.0;yi=0.98 0.92 0.81 0.64 0.38;x=-1:0.01:2;y1=Newton3(xi,yi,x; %源代碼見(jiàn)m文件pp=csape(xi,

2、yi, 'variational'y2=ppval(pp,x;plot(xi,yi,'o',x,y1,'r-',x,y2,'k'第二題MATLAB代碼：y1=zeros(1,11;x1=-1:0.2:1;for i=1:11,p=1./(1+25.*x1(i.2;y1(i=p;endx=-1:0.01:1;ym=language(x1,y1,x;yn=spline(x1,y1,x;y2=zeros(1,21;x2=-1:0.1:1;for i=1:21,p=1./(1+25.*x2(i.2;y2(i=p;endx=-1:0.01:

3、1;yi=language(x2,y2,x;yj=spline(x2,y2,x;figure(1;plot(x1,y1,'o',x,ym,'r-',x,yn,'k-'figure(2;plot(x2,y2,'o',x,yi,'r-',x,yj,'k-' 第三題MATLAB代碼：用spline進(jìn)行插值x1=0 1 4 9 16 25 36 49 64 ;y1=0 1 2 3 4 5 6 7 8;x=0:0.1:64;ym=language(x1,y1,x;yn=spline(x1,y1,x;figur

4、e(1;plot(x1,y1,'o',x,ym,'k-',x,yn,'r-'用scape用第一邊界條件進(jìn)行插值x1=0 1 4 9 16 25 36 49 64 ;y1=0 1 2 3 4 5 6 7 8;x=0:0.1:64;ym=language(x1,y1,x;pp=csape(x1,y1, 'complete',0.2,-1; yn=ppval(pp,x;figure(1;plot(x1,y1,'o',x,ym,'k-',x,yn,'r-'結(jié)論：0 64三次樣條插值精確0 1

5、多項(xiàng)式插值精確第三章第一題MATLAB代碼：y=zeros(1,11;x=-1:0.2:1;for i=1:11,p=1./(1+25.*x(i.2;y(i=p;endA=polyfit(x,y,3;y1=poly2str(A,'x'p1=-1:0.02:1;u1=polyval(A,p1;plot(p1,u1,x,y,'o'y1y1 =1.5271 x3 + 3.8235 x2 + 3.2599 x + 1.0023第二題MATLAB代碼：x=0.0 0.1 0.2 0.3 0.5 0.8 1.0;y=1.0 0.41 0.50 0.61 0.91 2.02 2.46;A1=polyfit(x,y,3;A2=polyfit(x,y,4;%用y=a*exp(b*x擬合u=log(y;A3=polyfit(x,u,1;m=A3(1;n=A3(2;a=exp(n;p1=-0.5:0.01:1.5;u3=a*exp(m*p1;u1=polyval(A1,p1;u2=polyv