I am in basic level in MATLAB , In the code i got the error as unrecoganised function or variable

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GEETHA NANIAPPAN
GEETHA NANIAPPAN 2021-9-7
评论： Sreedhar Arumugam 2021-9-7
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,'y-');
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,'y-',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;
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
ifi==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);
end
ux=(amat\B)';

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回答（1 个）

Abolfazl Chaman Motlagh
you use a function which is not introduced yet.
For every function, Create a New script, copy your function in it, save it with same name of the function in currect path of your project. after these steps you are able to call them.
for example, you use JSC1 before creating it.
function uu=JSC1(x,ap,cc)
uu=sin(cc*(x+ap));
end
save this to JSC1.m .
and you dont need necessarily to use them with feval. call them directly:
u0ex=JSC1(XX,0,cc);

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