ode45 with two variables

Hii Friends,

I have a variable delk which is [1*170001] matrix

I defined coupled equations as shown.

dB = zeros(3,170001); % a column vector

dB(1) = i*R*GammaL*B(3)*conj(B(2)).*exp(i.*delk*Z1); dB(2) = i*S*GammaL*B(3)*conj(B(1)).*exp(i.*delk*Z1); dB(3) = i*GammaL*B(1)*B(2).*exp(-i.*delk*Z1);

[Z1,B] = ode45(@(Z1,B) DFG789(Z1,B,delk),[0 3],[(0.1) 0 1]); plot3(delk,abs(B(:,1)).^2);

when i run the code i get the following errors. Any Suggestions?

In an assignment A(I) = B, the number of elements in B and I must be the same.

Error in DFG789 (line 41) dB(1) = i*R*GammaL*B(3)*conj(B(2)).*exp(i.*delk*Z1);

Error in @(Z1,B)DFG789(Z1,B,delk)

Error in odearguments (line 87) f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ode45 (line 113) [neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

Error in DFG7891 (line 28) [Z1,B] = ode45(@(Z1,B) DFG789(Z1,B,delk),[0 3],[(0.1) 0 1]);

[Torsten]

You still don't get it.

In the assignments

dB(1) = i*R*GammaL*B(3)*conj(B(2)).*exp(i.*delk*Z1);
dB(2) = i*S*GammaL*B(3)*conj(B(1)).*exp(i.*delk*Z1);
dB(3) = i*GammaL*B(1)*B(2).*exp(-i.*delk*Z1);

dB(1), dB(2), dB(3) are scalars, while the expressions on the right-hand side are vectors of length 1700001.

You could repair this by setting

dB(1:170001)=...
dB(170002:340002)=...
dB(340002:510003)=...

and by making the vector of initial values a 1x510003 - vector, but do you really want ODE45 solve 510003 ODEs simultaneously ? I think this is not a good idea.

Best wishes

Torsten.

[Torsten]

Your assignments would read

dB(1:170001)=i*R*GammaL*B(340003:510003)*conj(B(170002:340002)).*exp(i.*delk*Z1);
dB(170002:340002)=i*S*GammaL*B(340003:510003)*conj(B(1:170001)).*exp(i.*delk*Z1);
dB(340003:510003)=i*GammaL*B(1:170001).*B(170002:340002).*exp(-i.*delk*Z1);

and the initial condition vector

y0=zeros(510003);
y0(1:170001)=0.1;
y0(170002:340002)=0;
y0(340003:510003)=1;

Best wishes

Torsten.