n=input('/n 请输入分点数n: n=');x=-1:2/(n-1):1;fx=1./(1.+25.*x.^2);plot(x,fx,'ko');hold on;y=polyfit(x,fx,n-1);cs=csapi(x,fx);x=-1:0.01:1;yy=polyval(y,x);fx='1/(1+25*x^2)';fnplt(cs,'m-');hold on;fplot(fx,[-1,1],'b-');plot(x,yy,'g-');grid onlegend('original points','cubic spline curve','exact function','interpolating polynomials')x=-1:0.01:1;fx=1./(1.+25.*x.^2);yy=polyval(y,x);s=max(abs(fx-yy));fprintf('原函数与差值函数的最大误差为：');disp(s)x=-1:2/(n-1):1;fx=1./(1.+25.*x.^2);x1=-1:0.01:1;fx1=1./(1.+25.*x1.^2);s1=csapi(x,fx,x1);s=max(abs(s1-fx1));fprintf('三次样条函数与原函数的最大误差为：');disp(s)运行后??? Error using ==> run at 56Error: The input character is not valid in MATLAB statements or expressions.第2个！function coefs=cubicspline(x0,y0)m=length(x0);for i=1:m-1 h(i)=x0(i+1)-x0(i); endB=zeros(m-2,m-2);for i=1:m-2 for j=1:m-2 switch i-j case -1 B(i,j)=h(i+1); case 0 B(i,j)=2*(h(i)+h(i+1)); case 1 B(i,j)=h(i); end endendfor i=1:m-1 dd(i)=(y0(i+1)-y0(i))/(x0(i+1)-x0(i));endfor i=1:m-2 c(i)=6*(dd(i+1)-dd(i));endc=c';x1=B/c;A=zeros(m,m);A(2,1)=h(1);A(m-1,m)=h(m-1);for i=2:m-1 for j=2:m-1 switch i-j case -1 A(i,j)=h(i); case 0 A(i,j)=2*(h(i)+h(i-1)); case 1 A(i,j)=h(i-1); end endendA,b(1)=0;b(m)=0;for i=2:m-1 b(i)=6*(dd(i)-dd(i-1));endb=b',S1=[0.8;x1;0.2]; d=[0.8 0 0 0 0 0 0 0 0.2]';c1=c-d;x2=B/c1;S=[0.8;x2;0.2],fprintf('样条曲线的系数矩阵为：/n');for i=1:m-1 coef_a(i)=(S(i+1)-S(i))/(6*h(i)); coef_b(i)=S(i)/2; coef_c(i)=dd(i)-((2*h(i)*S(i)+h(i)*S(i+1))/6); coef_d(i)=y0(i);endcoefs=[coef_a',coef_b',coef_c',coef_d'];x=[];s=[];for i=1:m-1 xx=linspace(x0(i),x0(i+1),30); M=length(xx); for k=1:M ss(k)=coef_a(i)*(xx(k)-x0(i))^3+coef_b(i)*(xx(k)-x0(i))^2+coef_c(i)*(xx(k)-x0(i))+coef_d(i); end s=[s,ss]; x=[x,xx]; end plot(x0,y0,'*',x,s,'b-');grid on运行后??? Input argument "x0" is undefined.Error in ==> cubicspline at 2m=length(x0); 哪出问题了？
高手帮忙改一下！感激不尽```
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