Is there a way to impose positive domain on a selection of variables in odesolver

New to Julia
1

I am trying to solve 4 coupled differential equations the first two of them should always be positive while the 3rd and 4th can be positive or negative. I found that I can impose a positive domain on all four variables using

sol = solve(prob,AutoVern7(Rodas5()),callback=PositiveDomain(),reltol=1e-8,abstol=1e-8)

But is there a way to restrict the positive domain to a list of variables? Ideally, my plan is to work with a huge system where every third and fourth variable out of a few hundred has to be positive while others can be negative.

2

I think you should be able to use isoutofdomain. Something like

outofdomain(u, p, t) = u[1] < 0.0 || u[2] < 0.0

soln = solve(prob, ..etc; isoutofdomain=outofdomain)