数值分析(第五版)计算实习题第四章作业(6页).doc

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1、-第四章：1、（1）：复合梯形建立m文件：function t=natrapz(fname,a,b,n) h=(b-a)/n; fa=feval(fname,a);fb=feval(fname,b);f=feval(fname,a+h:h:b-h+0.001*h); t=h*(0.5*(fa+fb)+sum(f); 输入： syms x f=inline(sqrt(x).*log(x);); natrapz(f,eps,1,10)输出：ans = -0.417062831779470输入： syms x f=inline(sqrt(x).*log(x);); natrapz(f,eps,1,1

2、00)输出：ans = -0.443117908008157输入： syms x f=inline(sqrt(x).*log(x);); natrapz(f,eps,1,1000)输出：ans = -0.444387538997162复合辛普森建立m文件：function t=comsimpson(fname,a,b,n)h=(b-a)/n;fa=feval(fname,a);fb=feval(fname,b);f1=feval(fname,a+h:h:b-h+0.001*h);f2=feval(fname,a+h/2:h:b-h+0.001*h); t=h/6*(fa+fb+2*sum(f1

3、)+4*sum(f2);输入： syms x f=inline(sqrt(x).*log(x);); format long；comsimpson(f,eps,1,10)输出：ans = -0.435297890074689输入：syms xf=inline(sqrt(x).*log(x););comsimpson(f,eps,1,100)输出：ans = -0.444161178415673输入：syms xf=inline(sqrt(x).*log(x););comsimpson(f,eps,1,1000)输出：ans = -0.444434117614180 （2）龙贝格建立m文件：fu

4、nction RT,R,wugu,h=Romberg(fun,a,b,wucha,m) %RT是龙贝格积分表%R是数值积分值%wugu是误差估计%h是最小步长%fun是被积函数%a b是积分下、上限%m是龙贝格积分表中行最大数目%wucha是两次相邻迭代值的绝对误差限n=1;h=b-a;wugu=1;x=a;k=0;RT=zeros(4,4);RT(1,1)=h*(feval(fun,a)+feval(fun,b)/2;while(wuguwucha)&(km)|(kfun=inline(sqrt(x).*log(x); RT,R,wugu,h=Romberg(fun,eps,1,1e-5,1

5、3)输出：RT = 1 至 5 列 -0.000000268546145 0 0 0 0 -0.245064670140209 -0.326752804004897 0 0 0 -0.358104125949240 -0.395783944552250 -0.400386020588741 0 0 -0.408090073087781 -0.424752055467295 -0.426683262861631 -0.427100679405645 0 -0.429474601629505 -0.436602777810080 -0.437392825966266 -0.437562819031

6、419 -0.437603847029951 -0.438389494461832 -0.441361125405941 -0.441678348578999 -0.441746372747455 -0.441762778840459 6 列 0 0 0 0 0 -0.441766844267449R = -0.441766844267449wugu = 4.065426989774412e-06h = 0.031250000000000（3）自适应辛普森输入： f=inline(sqrt(x).*log(x); q=quad(f,0,1,1e-4)输出：q = -0.443975572951

7、7282.（1）复合辛普森建立m文件function q=combinesimpson2(F,x0,a,b,n)%复合Simpson多元求积公式%F被积函数%x0被积函数自变量%a,b积分区间%n区间份数x=linspace(a,b,n+1);q=0;for k=1:n q=q+subs(F,x0,x(k)+4*subs(F,x0,(x(k)+x(k+1)/2)+subs(F,x0,x(k+1);endq=q*(b-a)/n/6;输入： clear syms x y; F=exp(-x.*y); s=combinesimpson2(combinesimpson2(F,x,0,1,4),y,0,

8、1,4)输出：s = exp(-1)/576 + exp(-1/2)/144 + exp(-1/4)/72 + exp(-3/4)/144 + exp(-1/8)/36 + exp(-3/8)/36 + exp(-5/8)/72 + exp(-7/8)/72 + (5*exp(-1/16)/144 + exp(-3/16)/24 + exp(-5/16)/36 + exp(-7/16)/36 + exp(-9/16)/144 + exp(-1/32)/36 + exp(-3/32)/18 + exp(-5/32)/36 + exp(-7/32)/36 + exp(-9/32)/36 + exp

9、(-15/32)/36 + exp(-21/32)/36 + exp(-1/64)/36 + exp(-3/64)/18 + exp(-5/64)/18 + exp(-7/64)/18 + exp(-9/64)/36 + exp(-15/64)/18 + exp(-21/64)/18 + exp(-25/64)/36 + exp(-35/64)/18 + exp(-49/64)/36 + 47/576 double(s)ans = 0.796599967946203高斯求积公式function q=gaussquad(F,x0,a,b,n)%Gauss求积公式%F被积函数%x0被积函数自变量%

10、a,b积分区间%n节点个数syms t;F=subs(F,x0,(b-a)/2*t+(a+b)/2);x,A=gausspoints(n);q=(b-a)/2*sum(A.*subs(F,t,x);输入： clear syms x y;F=exp(-x.*y); s=gaussquad(gaussquad(F,x,0,1,4),y,0,1,4)输出：s =0.7966（2）复合辛普森输入： syms x y; f=exp(-x.*y); s=combinesimpson2(combinesimpson2(f,y,0,sqrt(1-x2),4),x,0,1,4) 输出：s = (3(1/2)*(

11、exp(-3(1/2)/4) + 2*exp(-3(1/2)/8) + 2*exp(-3(1/2)/16) + 2*exp(-(3*3(1/2)/16) + 4*exp(-3(1/2)/32) + 4*exp(-(3*3(1/2)/32) + 4*exp(-(5*3(1/2)/32) + 4*exp(-(7*3(1/2)/32) + 1)/576 + (7(1/2)*(exp(-(3*7(1/2)/16) + 2*exp(-(3*7(1/2)/32) + 2*exp(-(3*7(1/2)/64) + 2*exp(-(9*7(1/2)/64) + 4*exp(-(3*7(1/2)/128) +

12、4*exp(-(9*7(1/2)/128) + 4*exp(-(15*7(1/2)/128) + 4*exp(-(21*7(1/2)/128) + 1)/1152 + (15(1/2)*(exp(-15(1/2)/16) + 2*exp(-15(1/2)/32) + 2*exp(-15(1/2)/64) + 2*exp(-(3*15(1/2)/64) + 4*exp(-15(1/2)/128) + 4*exp(-(3*15(1/2)/128) + 4*exp(-(5*15(1/2)/128) + 4*exp(-(7*15(1/2)/128) + 1)/1152 + (15(1/2)*(exp(

13、-(7*15(1/2)/64) + 2*exp(-(7*15(1/2)/128) + 2*exp(-(7*15(1/2)/256) + 2*exp(-(21*15(1/2)/256) + 4*exp(-(7*15(1/2)/512) + 4*exp(-(21*15(1/2)/512) + 4*exp(-(35*15(1/2)/512) + 4*exp(-(49*15(1/2)/512) + 1)/1152 + (39(1/2)*(exp(-(5*39(1/2)/64) + 2*exp(-(5*39(1/2)/128) + 2*exp(-(5*39(1/2)/256) + 2*exp(-(15*

14、39(1/2)/256) + 4*exp(-(5*39(1/2)/512) + 4*exp(-(15*39(1/2)/512) + 4*exp(-(25*39(1/2)/512) + 4*exp(-(35*39(1/2)/512) + 1)/1152 + (55(1/2)*(exp(-(3*55(1/2)/64) + 2*exp(-(3*55(1/2)/128) + 2*exp(-(3*55(1/2)/256) + 2*exp(-(9*55(1/2)/256) + 4*exp(-(3*55(1/2)/512) + 4*exp(-(9*55(1/2)/512) + 4*exp(-(15*55(1/2)/512) + 4*exp(-(21*55(1/2)/512) + 1)/1152 + (63(1/2)*(exp(-63(1/2)/64) + 2*exp(-63(1/2)/128) + 2*exp(-63(1/2)/256) + 2*exp(-(3*63(1/2)/256) + 4*exp(-63(1/2)/512) + 4*exp(-(3*63(1/2)/512) + 4*exp(-(5*63(1/2)/512) + 4*exp(-(7*63(1/2)/512) + 1)/1152 + 1/24 double(s)ans = 0.670113633359095-第 6 页-