Hi,
I've solved a simple differential equation describing the degradation of
amino acid carbon (THAA-C) using deSolve.
Code is a follows:
# Input of model parameters, a and b describes form of curve, i is apparent
initial age of Org. C.
parameters <- c(a = a, b = b, i=i)
# Initial value of the model, G
state = c(G = G)
#specifies the function degradation as a function of time (t), inital state
(state) and parameters (given parameters in model)
degradation = function (t, state, parameters) {
#Specifies that state an parameters is inputted as lists, hence order in the
lists is important
with(as.list(c(state, parameters)),
#differential equation to be solved
{dG = (-a*(t+i)^b)*(G)
list(c(dG))
})
}
# Makes sequence of times to be solved for. Start at t0 and proceed to iteno
in steps of 1 day
times = seq(t0, iteno, by = 1)
#calls solver, to solve diffrential equation and saves results as variable
THAAC
THAAC = ode (y = state, times = times, func = degradation, parms =
parameters)
This all works fine, and output THAAC contains carbon concentrations of G at
all times t. However, i would like the model to give me the rates, i.e. dG
for all times. And possibly also the value of -a*(t+i)^b for all times.
Does anyone know if this is possible?
Kristoffer Piil
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