I am having error in this programme. i gave the call function also.

16 次查看（过去 30 天）
GEETHA NANIAPPAN
GEETHA NANIAPPAN 2021-9-15
评论： Walter Roberson 2021-9-15
Nx=41;XL=0;XR=2*pi;
dx=(XR-XL)/(Nx-1);
for i=1:Nx
XX(i)=XL+(i-1)*dx;
end
cfl=0.125;dt=cfl*dx^3;tlast=1;
Nstep=tlast/dt;
cc=1;
IRK=4;
[u0ex]=feval(@JSC1,XX,0,cc);
uold=u0ex;
subplot(2,1,1),plot(XX,u0ex,'k-');
hold on
for k=1:Nstep
if IRK==4
u0x=reconuxxxp(uold,Nx,dx);
k0=dt*resJSC1(uold,u0x,cc);
u1=uold+k0/2;
u1X=reconuxxxp(u1,Nx,dx);
k1=dt*resJSC1(uold,u1x,cc);
u2=uold+k1/2;
u2x=reconuxxxp(u2,Nx,dx);
k2=dt*resJSC1(uold,u2x,cc);
u3=uold+k2;
u3x=reconuxxxp(u3,Nx,dx);
k3=dt*resJSC1(uold,u3x,cc);
unew=uold+(k0+2*k1+2*k2+k3)/6;
elseif IRK==2
u0x=reconuxp(uold,Nx,dx);
u0xx=reconuxp(u0x,Nx,dx);
u0xxx=reconuxp(u0xx,Nx,dx);
u2x=reconuxp(uold.^2,Nx,dx);
ko=dt*resJSC1(u2x,u0xxx,cc);
u1=uold+k0;
u1x=reconuxp(u1,Nx,dx);
uxx=reconuxp(u1x,Nx,dx);
uxxx=reconuxp(uxx,Nx,dx);
u2x=reconuxp(u1.^2,Nx,dx);
k1=dt*resJSC1(u2x,uxxx,cc);
u2=u1+k1;
unew=(uold+u2)/2;
end
uold=unew;
eps=0.3*dt;
if abs(k*dt-0.25)<eps|abs(k*dt-0.5)<eps|abs(k*dt-0.75)<eps|abs(k*dt-1)<eps disp(k),
[u0ex]=feval(@JSC1,XX,k*dt,cc);
subplot(2,1,1),plot(XX,unew,'b-',XX,uoex,'g.');
xlabel('x');ylabel('u(x,t)');
hold on
subplot(2,1,2),
if abs(k*dt-0.25)<eps,plot(XX,abs(u0ex-unew),'r-');end
if abs(k*dt-0.5)<eps,plot(XX,abs(u0ex-unew),'r-.');end
if abs(k*dt-0.75)<eps,plot(XX,abs(u0ex-unew),'r--');end
if abs(k*dt-1)<eps,plot(xx,abs(u0ex-unew),'r:');end
xlabel('x');ylabel('inf error');
hold on
end
end
function uu=JSC1(x,ap,cc)
uu=sin(cc*(x+ap));
function uu=resJSC1(u1,u2,cc)
uu=-cc*u2;
function ux=reconuxxxp(u,N,h)
IEX=0;
if IEX==4
a=2;b=-1;
for i=1:N
if i==1
tmp=b*(u(i+3)-3*u(i+1)+3*u(N-1)-u(N-3))/4+a*(u(i+2)-2*u(i+1)+2*u(N-1)-u(N-2));
else if i==2
tmp=b*(u(i+3)-3*u(i+1)+3*u(i-1)-u(N-2))/4+a*(u(i+2)-2*u(i+1)+2*u(i-1)-u(N-1));
else if i==3
tmp=b*(u(i+3)-3*u(i+1)+3*u(i-1)-u(N-1))/4+a*(u(i+2)-2*u(i+1)+2*u(i-1)-u(i-2));
else if i==(N-2)
tmp=b*(u(2)-3*u(i+1)+3*u(i-1)-u(i-3))/4+a*(u(i+2)-2*u(i+1)+2*u(i-1)-u(i-2));
else if i==(N-1)
tmp = b*(u(3)-3*u(i+1)+3*u(i-1)-u(i-3))/4+a*(u(2)-2*u(i+1)+2*u(i-1)-u(i-2));
else if i==N
tmp=b*(u(4)-3*u(2)+3*u(i-1)-u(i-3))/4+a*(u(3)-2*u(2)+2*u(i-1)-u(i-2));
else
tmp=b*(u(i+3)-3*u(i+1)+3*u(i-1)-u(i-3))/4+a*(u(i+2)-2*u(i+1)+2*u(i-1)-u(i-2));
end
ux(i)=tmp/(2*h^3);
end
return
end
if IEX==6
a=-488/240;b=338/240;c=-72/240;d=7/240;
for i=1:N
if i==1
tmp=a*(u(i+1)-u(N-1))+b*(u(i+2)-u(N-2))+c*(u(i+3)-u(N-3))+d*(u(i+4)-u(N-4));
else if i==2
tmp=a*(u(i+1)-u(i-1))+b*(u(i+2)-u(N-1))+c*(u(i+3)-u(N-2))+d*(u(i+4)-u(N-3));
else if i==3
tmp=a*(u(i+1)-u(i-1))+b*(u(i+2)-u(i-2))+c*(u(i+3)-u(N-1))+d(u(i+4)-u(N-2));
else if i==4
tmp=a*(u(i+1)-u(i-1))+b*(u(i+2)-u(i-2))+c*(u(i+3)-u(i-3))+d*(u(i+4)-u(N-1));
else if i==(N-3)
tmp=a*(u(i+1)-u(i-1))+b*(u(i+2)-u(i-2))+c*(u(i+3)-u(i-3))+d(u(2)-u(i-4));
else if i==(N-2)
tmp=a*(u(i+1)-u(i-1))+b*(u(i+2)-u(i-2))+c*(u(2)-u(i-3))+d*(u(3)-u(i-4));
else if i==(N-1)
tmp=a*(u(i+1)-u(i-1))+b*(u(2)-u(i-2))+c*(u(3)-u(i-3))+d*(u(4)-u(i-4));
else if i==N
tmp=a*(u(2)-u(i-1))+b*(u(3)-u(i-2))+c*(u(4)-u(i-3))+d*(u(5)-u(i-4));
else
tmp=a*(u(i+1)-u(i-1))+b*(u(i+2)-u(i-2))+c*(u(i+3)-u(i-3))+d*(u(i+4)-u(i-4));
end
ux(i)=tmp/(h^3);
end
return
end
ISC=6;
if ISC==4
alfa=15/32;aa=2;bb=2*alfa-1;
else if ISC==6
alfa=7/16;aa=2;bb=-1.0/8;
end
amat=zeros(N,N);
B=zeros(N,1);
for i=1:N
if i==1
amat(1,1)=1;amat(1,2)=alfa;amat(1,N-1)=alfa;
B(i)=bb*(u(i+3)-3*u(i+1)+3*u(N-1)-u(N-3))/4+aa*(u(i+2)-2*u(i+1)+2*u(N-1)-u(N-2));
else if i==2
amat(2,1)=alfa;amat(2,2)=1;amat(2,3)=alfa;
B(i)=bb*(u(i+3)-3*u(i+1)+3*u(i-1)-u(N-2))/4+aa*(u(i+2)-2*u(i+1)+2*u(i-1)-u(N-1));
else if i==3
amat(i,i-1)=alfa;amat(i,i)=1;amat(i,i+1)=alfa;
B(i)=bb*(u(i+3)-3*u(i+1)+3*u(i-1)-u(N-1))/4+aa*(u(i+2)-2*u(i+1)+2*u(i-1)-u(i-2));
else if i==N-2
amat(i,i-1)=alfa;amat(i,i)=1;amat(i,i+1)=alfa;
B(i)=bb*(u(2)-3*u(i+1)+3*u(i-1)-u(i-3))/4+aa*(u(i+2)-2*u(i+1)+2*u(i-1)-u(i-2));
else if i==N-1
amat(i,i-1)=alfa;amat(i,i)=1;amat(i,i+1)=alfa;
B(i)=bb*(u(3)-3*u(i+1)+3*u(i-1)-u(i-3))/4+aa*(u(2)-2*u(i+1)+2*u(i-1)-u(i-2));
else if i==N
amat(N,1)=-1;amat(N,N)=1;
B(i)=0
else
amat(i,i-1)=alfa;amat(i,i)=1;amat(i,i+1)=alfa;
B(i)=bb*(u(i+3)-3*u(i+1)+3*u(i-1)-u(i-3))/4+aa*(u(i+2)-2*u(i+1)+2*u(i-1)-u(i-2));
end
B(i)=B(i)/(2*h^3);
ux=(amat\B)';
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
end
  1 个评论
KSSV
KSSV 2021-9-15
What error you are getting? Your ocde has got lot of loops. I think there is a lot of room to make your code effective.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Walter Roberson
Walter Roberson 2021-9-15
The function you are missing is on PDF page 108 of https://www.researchgate.net/file.PostFileLoader.html?id=5696da346143257e508b4567&assetKey=AS%3A317578013020160%401452727906601

类别

在 Help Center 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息

标签

产品

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by