Can the output be a ratio between state variables like: y(t) = x(t)/(S(t)+E(t)+x(t))?

[qchenmath]

For all the examples, the output(s) are always simple function of the state variables. Will it work if the output is as given in the title? Thanks.

[sumiya11]

Hi @qchenmath . Yes, ratios in the output should work.

For example,

using StructuralIdentifiability
ode = @ODEmodel(
           x'(t) = a*x,
           y(t) = x^2 // (x + a + 1)
       )
assess_identifiability(ode)

Note the double slash. (edit: perhaps / works as well)

[pogudingleb]

Thanks, @sumiya11 !
Indeed, single slash for division is fine.

[qchenmath]

Thanks. Guess the model is somewhat complicated. It didn't finish after 5 days, and I had to kill it.

[pogudingleb]

@qchenmath
Yes, this may happen, especially with fractions. Feel free to send me the model to look at, I might be able to propose something to speed up the calculations.
Note that you can also always get at least local identifiability info with assess_local_identifiability function.