Degradation model

Dear list,

I have a degradation model:

dX/dt = * I(X2)*( k1*X(t) )/( X(t)+k2 ) 

where X(t) is concentration at time t, and k1 and k2 are parameters
that I want to estimate. I(X) is a known inhibitor function.

My questions is whether this is implemented or easily computed in any
R package. I have searched the archives but without luck.


Any help or comments on this would be appreciated,
Klaus Andersen