How to apply if statement in ode45 function?

I have a multiple equations with variables c1, c2, c3.

Each variables decrease as the time increases.

And I want to put if statement in the function of ode for example "If c1 < 0, then c1 = 0."

I tried as follows:

[t, c] = ode45(@(t,c) myode(t,c), tspan, c0);

function dcdt = myode(t,c)

dcdt = zeros(3,1);

if c(1) < 0

c(1) = 0

end

dcdt(1) = ...

dcdt(2) = ...

dcdt(3) = ...

end

====> It doesn't work : How could I apply if statement properly in this case??

Answer 1

[Stephen23]

c = max(0,c);

[kkh1897]

where can I put c=max(0,c)?

In the function? or before ode45 expression?

Can you explain it in detail?

Thank you