[R] Fitting a System of Difference Equations
mo2259 at columbia.edu
Tue Jun 17 06:46:35 CEST 2008
Hi R friends,
I’m interested in fitting data to the following system of difference
Change in M = k*(1-M.prev)*(1-F.prev) + R*(1-M.prev)*F.pref
Change in F = k*(1-F.prev)*(1-M.prev) + S*(1-F.prev)*M.pref
k, R, S, are transition rates
M = Proportion of Males Sexually Active
F = Proportion of Females Sexually Active
M.prev and F.prev are the t-1 values of M and F.
The modeling of this in R is straightforward. However, I’d like to fit
the simulation to actual prevalence data such that I’m iteratively
honing in on the three parameters, given my starting prevalence values,
via some loss function. I’m thinking of using <nls> for this but in some
way replacing the right side of the formula specification with a
function that calls the system of equations. But, I’m not sure this will
work and I don’t know how to do this (I’ve done a thorough search on R
and Google, without luck).
Any help or direction would be much appreciated.
More information about the R-help