I am using the ode15s solver with the cantera's library. I came across this error (see below) that I don't know how to solve. Many thanks for the help.

This is my main code:

y = [20 5 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0];

biopyrolysis  = IdealGasMix('biomass_cell.xml');

p = pressure(biopyrolysis);

options = odeset('OutputFcn',{@odeplot,@odeprint});

options = odeset(options,'RelTol',1.e-5,'AbsTol',1.e-9);

tspan = [1 5];

for nt = 1:20;

      out = ode15s(@reactor_ode,tspan,y,options,biopyrolysis);

end

and these are my functions:

function dydt = reactor_ode(t,y,gas)

[m,n] = size(y);

dydt = zeros(m,n);

for j = 1:n

      this_y = y(:,j);
      int_energy = this_y(1);
      vol = this_y(2);
      masses = this_y(3:end);

      % evaluate the total mass, and the specific internal energy and volume.
      total_mass = sum(masses);
      u_mass = int_energy/total_mass;
      v_mass = vol/total_mass;

      % set the state of the gas by specifying (u,v,{Y_k})
      setMassFractions(gas,masses);
      setState_UV(gas, [u_mass v_mass]);
      p = pressure(gas);

      % volume equation
      vdt = feval(@vdot, t, vol, gas);

      % energy equation
      a = feval(@area, t, vol);
      q = feval(@heatflux, t, gas);
      udt = -p * vdt + a * q;

      % species equations
      ydt = total_mass * ydot(gas);

      % set up column vector for dydt
      dydt(:,j) = [udt
          vdt
          ydt ];
  end

function q = heatflux(t, gas)

q = 0.0;                               

end

function a = area(t,vol)

a = 1.0;

end

function v = vdot(t, vol, gas)

v = 1.e11 * (pressure(gas) - 101325.0);   

end

and the error I get is:

Error using feval

Argument must contain a string or function_handle.

Error in ode15s (line 481)

    feval(outputFcn,[t tfinal],y(outputs),'init',outputArgs{:});

Error in test (line 15)

      out = ode15s(@reactor_ode,tspan,y,options,biopyrolysis);

But the way I see, all the functions I am using are handle.

Answer 1

[Walter Roberson]

The difficulty is in evaluating the OutputFcn, which you have created as {@odeplot,@odeprint} which is a cell array of function handles rather than being one function handle. If you look at https://www.mathworks.com/help/matlab/ref/odeset.html#input_argument_namevalue_OutputFcn you will see that the documented syntax is

[] or @odeplot (default) | function handle

which does not permit a cell array of function handles.

[Isabel]

it worked :) Many, many thanks!!