\(\cal X\) Component Derivatives for the SIS Model

Compute the derivatives for SIS compartmental model, defined as: $$ \begin{array}{rcccc} dS/dt =& - h S &+ r I &+ d{\cal H}(S) &+ B(t, H) \\ dI/dt =& h S & - r I &+ d{\cal H}(I) \end{array} $$ where \(H = S+I\); \(B(t, H)\) is the time-dependent birth rate; and the \(d{\cal H}\) operator computes derivatives for the demographic model \(\cal H\).

# S3 method for class 'SIS'
dXdt(t, y, pars, i)

Arguments

t

current simulation time

y

state vector

pars

an xds object

i

the host species index

Value

a numeric vector