chengxuwenjian.rar_一维有限元_有限元解_有限元解方程

function [wucha1]= ww(funfcn,N,n) syms x1 x2 x ; L=1; h=L/N; wucha2=0; B=zeros(N,2); B(:,1)=(1:1:N)'; B(:,2)=(2:1:N+1)'; W=(0:h:1)'; s=(2:1:N)'; A=zeros(N+1); b=zeros(N+1,1); u=zeros(N+1,1); ss=0; s2=0; s1=0; s0=0; ss1=0; for i=1:N jd=B(i,:); x1=W(jd(1));x2=W(jd(2)); Q1=(x2-x)/(x2-x1); Q2=(x-x1)/(x2-x1); dQ1=diff(Q1,x); dQ2=diff(Q2,x); ae=[int(dQ1*dQ1,x,x1,x2) int(dQ1*dQ2,x,x1,x2); int(dQ2*dQ1,x,x1,x2) int(dQ2*dQ2,x,x1,x2)]; be=[int(Q1*x,x,x1,x2);int(Q2*x,x,x1,x2)]; A(jd,jd)=A(jd,jd)+ae; b(jd)=b(jd)+be; end Aa=A(s,s); %结点1固定，删去矩阵第一、五行第一、五列 ba=b(s); ua=Aa\ba; u(s)=ua; %绘图效果 for i=1:N uh=u(i)*(i-x/h)+u(i+1)*(x/h-i+1); u0=x/6-x^3/6; z=(u0-uh)^2; z1=diff(u0-uh); z2=z1^2; dx=h/n; xx=h*(i-1):dx:h*i; for j=1:n f1=subs(z,x,xx(j)); f2=subs(z,x,xx(j+1)); yy=(xx(j)+xx(j+1))/2; f12=subs(z,x,yy); ss=ss+dx*(f1+f2+4*f12)/6; g1=subs(z2,x,xx(j)); g2=subs(z2,x,xx(j+1)); yy=(xx(j)+xx(j+1))/2; g12=subs(z2,x,yy); ss1=ss1+dx*(g1+g2+4*g12)/6; end s2=sum(ss);s1=sum(ss1);s0=s1+s2; end wucha1=sqrt(s0);