MATLAB: Error in Ode 45

ode45

I have a probleb solving this ode ODE it gives me the following errors
or too many inputs in the ode45
or Inputs must be floats, namely single or double.
burn_time=100;
Nt=1000;
m_ox=0.7;
t=linspace(0,burn_time,Nt);
m_ox=m_ox.*ones(1,Nt);
Dp_in=0.0005;
rho_fuel=1.9;
L_grain=0.5;
%% Definizione regression rate
a=0.007;
b=0.67;
r_dot=a.*m_ox.^b;% in futuro r_dot sara gia fornito da dati sperimentali
C=((m_dot_fuel+m_ox-m_dot_pr)./(v_cham)) ;
A=((4.*r_dot)./Dp_t);
dt=t(2)-t(1);
t_span=(0:dt:burn_time);
y_0=zeros(1,Nt);
y_0=y_0(:);
[T,Y ]=ode45(@(t,y) vdp1(C,y,A),t_span,y_0);
function dydt = vdp1(C,y,A)
dydt =C+A*y;
dydt=dydt(:);
end

Best Answer

The problem here: 
[T,Y ]=ode45(@(t,y) vdp1(C,y,A),t_span,y_0);
is that one of the input arguments to ‘vdp1’ needs to be ‘t’.
There are too many missing constants for me to run your code, however this: 
[T,Y ]=ode45(@(t,y) vdp1(t,C,y,A),t_span,y_0);
should work, if there are no other problems.
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