计算方法书中的MATLAB实例PPT学习课件

1、用Matlab实现求积分,在Matlab程序编辑器中输入：,y0=log(6.0/5.0);fprintf(y%d=%fn,0,y0)n=1;while(1)yl=1.0/n-5*y0;fprintf(y%d=%fn,n,yl)if(n=20)break;endy0=yl;n=n+1;end,1,2020/7/4,2,2020/7/4,程序运行结果:,3,2020/7/4,functionx=nabisect(fname,a,b,e)%fname为内嵌函数表达式；a,b为区间端点；e为输入定义的精度ifnargin0,error(函数在两端点值必须异号);endx=(a+b)/2while(b

2、-a)(2*e)fx=feval(fname,x);iffa*fx0,b=x;fb=fx;elsea=x;fa=fx;endx=(a+b)/2end,程序如下：,Matlab应用举例(二分法),4,2020/7/4,5,2020/7/4,程序运行结果：,6,2020/7/4,用Matlab实现Newton迭代法求解,functionx=nanewton(fname,dfname,x0,e,N)ifnargineend,程序如下：,7,8,2020/7/4,程序运行结果：,9,2020/7/4,10,2020/7/4,%回代x=zeros(n,1);x(n)=a(n,n+1)/a(n,n);fo

3、rk=n-1:-1:1x(k,:)=(a(k,n+1)-a(k,(k+1):n)*x(k+1):n)/a(k,k);end,11,2020/7/4,12,2020/7/4,程序运行结果：,13,2020/7/4,14,2020/7/4,ifflag=0,a,endend%回代x=zeros(n,1);x(n)=a(n,n+1)/a(n,n);fork=n-1:-1:1x(k,:)=(a(k,n+1)-a(k,(k+1):n)*x(k+1):n)/a(k,k);end,15,2020/7/4,16,2020/7/4,程序运行结果:,17,2020/7/4,用Matlab实现LU分解,在Matla

4、b程序编辑器中输入：,functionL,U=nalu(a)%a为可逆方阵；L返回单位下三角矩阵；U返回上三角矩阵n=length(a);U=zeros(n,n);L=eye(n,n);U(1,:)=a(1,:);L(2:n,1)=a(2:n,1)/U(1,1);fork=2:nU(k,k:n)=a(k,k:n)-L(k,1:k-1)*U(1:k-1,k:n);L(k+1:n,k)=(a(k+1:n,k)-L(k+1:n,1:k-1)*U(1:k-1,k)/U(k,k);end,18,2020/7/4,19,2020/7/4,程序运行结果:,20,2020/7/4,21,2020/7/4,22,2020/7/4,求解例题得一次插值和二次插值如右图所示：,23,2020/7/4,24,2020/7/4,25,2020/7/4,最小二乘拟合多项式结果如右图:,26,2020/7/4,27,2020/7/4,28,2020/7/4,Euler