[R] Difficulty in writing R code for one pool dynamic model
Kebebe Ergano
kebeberg @ending from y@hoo@com
Tue May 29 02:02:49 CEST 2018
Hi everyone,
I was trying to mode the following exercise using R.
The question: Set up a one pool model using numericintegration. The model will run from time 1 to time 30 using a time step of 1.The pool (A) will be fed by flux "inA" at a rate of 5 units per hour anddrained by flux "outA" at a rate of 20% per hour. At time 0, A has 5units. At time 30, what is the pool size of A (rounded to 1 decimal)? In theanswer sheet provide the value of pool could be (23.8, 24.8, 25.0 or 24.7). Thevalue I got does not correspond to any of the choices given above. I don't know where I got it wrong.
Below is the Ro code I tried to estimate thepool size of A at time 30.
#Step 1: Specify time
Tstart <- 1
Tstop <- 30
Tstep <- 1
#Step 2: Set variables corresponding to pools
inA<-5
A <- inA
t <- Tstart
#Step 3: Set up rate parameters
A<-5
kinA <- 5
koutA <- 0.2
#Step 4: Write arrays that track pool size overtime
val <- array(1, dim=c(1, length(seq(Tstart,Tstop, by=Tstep))))
val
#Step 5: Set up while loop we use to runintegration
while(t<=Tstop){
if(t==Tstart) A <- inA else A <- val[1, t-1]
# Setup rates
inA<- kinA*A
outA<- A*koutA
A <-A+inA-outA
val[1,t] <- A
t <-t+1
}
# Step 6: Print the output as array
value <- data.frame(val)
# Transpose 'value' using t
value <- t(value)
value
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