Solving an ODE numerically .. What is the problem in my code?

Hello,

I want to solve this ODE numerically..

dq_pl/dt=f_plc*R_c*N_c0*exp(K_gr*t)+f_plh*R_h*N_h0-K_el*q_pl(t).

Where the letters following the underscore signs are subscripts, the parameters values are:

fplc=0.1 ; Rc=4.5*10^-5 ; Nc0=1 ; Kgr= 5.78*10^-3 ; fplh*Rh*Nh=4.56*10^3 ; Kel= 0.11 ;

 tspan = [0 10^10] , qpl0 = 0

I wrote:

function [t,qpl] = call_dstate()
 tspan = [0 10^10]; % set time interval
 qpl0 = 0; % set initial condition
 % dstate evaluates r.h.s. of the ode
 [t,qpl] = ode45( @dstate ,tspan ,qpl0);
 plot(t,qpl)
 disp([t,qpl]) % displays t and qpl(t)
       function dqpldt = dstate (t,qpl)
             fplc=0.1 ; Rc=4.5*10^-5 ; Nc0=1 ; Kgr= 5.78*10^-3 ; fplh*Rh*Nh=4.56*10^3 ; Kel= 0.11 ;
             dqpldt=fplc*Rc*Nc0*exp(Kgr*t)+fplh*Rh*Nh0-Kel*qpl;
       end
end

Thanks in advance.

[John D'Errico]

Why do you think there is a problem? Did an error occur?

[Esraa Abdelkhaleq]

yes, the error appears as:

Error: Unexpected MATLAB expression.

Answer 1

[Torsten]

Use fplh_Rh_Nh instead of fplh*Rh*Nh:

fplh_Rh_Nh = 4.56e3;
...
dqpldt=fplc*Rc*Nc0*exp(Kgr*t)+fplh_Rh_Nh0-Kel*qpl

Best wishes

Torsten.

[Esraa Abdelkhaleq]

Dear Torsten,

Thanks a lot.

I did what you said but the same error appeared !

May I have a problem in the version itself? how can I check that everything is OK in the version? I use 2008a version.

[Torsten]

Use

dqpldt=fplc*Rc*Nc0*exp(Kgr*t)+fplh_Rh_Nh-Kel*qpl

Best wishes

Torsten.