> On May 28, 2018, at 5:02 PM, Kebebe Ergano via R-help <

[hidden email]> wrote:

>

>

> 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.

>

Homework is not on-topic for r-help. Nevertheless you might try using a small time increment if you are being asked to do numeric integration. You also might look up the many worked examples of compound interest.

David.

> 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

>

>

>

> [[alternative HTML version deleted]]

>

> ______________________________________________

>

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https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide

http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.