5.m

利用龙格库塔法（等步长

clear all
a=0;b=10;
for j=1:4
    N=10*2^(j-1)
    h=(b-a)/N
    k=0.5;
    v=0;
    c=1;
    p=1;
    q0=50;
    T0=400;
    Tout=300;
    kv=10;
    l=1;m=3;
    xp=a:h:b+h;
    n=2;
    for x=a+h:h:l
        f(n)=0;
        n=n+1;
    end
    for x=l+h:h:m
    f(n)=q0*sin((x-l)/(m-l)*pi)*h^2;
    n=n+1;
    end
    for x=m+h:h:b
        f(n)=0
        n=n+1;
    end
    f(1)=T0;
    f(n)=-2*kv*h*Tout
    A=zeros(N,N);
    A(1,1)=1;
    for i=2:N+1
        A(i,i-1)=-2*k-v*p*c*h;
        A(i,i)=4*k;
        A(i,i+1)=-2*k+v*p*c*h;
    end
    A(N+2,N)=k;
    A(N+2,N+1)=-2*kv*h;
    A(N+2,N+2)=-k
        u=A\f';
    up=[u']

  if j==1
    plot(xp,up,'b')
    hold on
elseif j==2
    plot(xp,up,'g')
    hold on
elseif j==3
    plot(xp,up,'r')
    hold on
  else
      plot(xp,up,'m')
end
end