Function of boundary conditions PDEPE

Hi! I want to set the boundary conditions for a heat transfer parabolic pde using the function PDEPE and the already curve fitted model interpol.mat (which has a function called fittedmodel that returns the temperature T at the time t, f.ex. fittedmodel(20)=300) as the temperature of the left and of the right wall, but it seems it does not work this way:

function [pl,ql,pr,qr] = pdex1bc(xl,ul,xr,ur,t)

load('interpol.mat'); 

pl=fittedmodel(t);
pr=fittedmodel(t);
ql=0;
qr=1;

The following error occurs:

Error using daeic12 (line 77)
This DAE appears to be of index
greater than 1.

Error in ode15s (line 311)
    [y,yp,f0,dfdy,nFE,nPD,Jfac] =
    daeic12(odeFcn,odeArgs,t,ICtype,Mt,y,yp0,f0,...

Error in pdepe (line 317)
  [t,y] = ode15s(@pdeodes,t,y0,opts);

Error in pdemytry (line 45)
sol =
pdepe(m,@pdex1pde,@pdex1ic,@pdex1bc,x,t);

Thank you!

Answer 1

[Bill Greene]

To set the temperature at each end to fittedmodel(t), you would define:

pl = ul-fittedmodel(t);
pr = ur-fittedmodel(t);

Take a look at the boundary condition equation 1-6 on this page pdepe

Bill

[Ignacio]

Thank you I will!