Coupled ODE using ODE15s with multiple outputs

I am looking to solve 2 sets of coupled ODEs (one with dCp1 and the other with dQp1). When I try to use OD15s using,t,Cp1,Qp1] = ode15s(@solver4,[0,15],horzcat(zeros([1,100]))), I get an error message "[Cp1,Qp1] = ode15s(@solver4,[0,15],zeros(1,100))".

Is there a way for ODE15s to solve these 2 sets of coupled ODEs?

function [dCp1 dQp1] = solver4(t,Cp1,Qp1)

n=100;
D=0.008;
u=1;
dCp1=zeros(n,1);
V=1/n;

Qp1(1)=1;
dQp1=zeros(n,1);

kads=1;
kdes=1;

if t<0.1
    Cp1(1)=1;
else 
    Cp1(1)=0;
end

for i=2:n-1
    dCp1(i)=D*((Cp1(i-1)-2*Cp1(i)+Cp1(i+1))/(V^2))+u*((Cp1(i-1)-Cp1(i))/V)-(Qp1(i)-Qp1(i-1))/V;
    dQp1(i)=kads*Cp1(i)-kdes*Qp1(i);
end
dCp1(n)=(Cp1(n-1)-Cp1(n))/V;
dQp1(n)=kads*Cp1(n)-kdes*Qp1(n);
end   

Answer 1

[Torsten]

When communicating with ODE15S, the solution must be treated as one vector of size 200, not as two vectors of size 100.

E.g.

function [dCQ] = solver4(t,CQp)
  n = 100;
  Cp1 = CQp(1:n);
  Qp1 = CQp(n+1:2*n);
  dCp1 = zeros(n,1);
  dQp1 = zeros(n,1);
  ...
  dCQ = [dCp1;dQp1];
end

[Nicholas Vecchiarello]

Thank you!!