R help - May 2011 - dynamic programming

Dear members of R forum,

I'm trying to perform a simply dynamic programming model in R, following the
reccomendations of Soetart & Herman (A practical guide to ecological
modeling). However, I've obtained a number of problems, that I'm unable
to
solve (even thoughI've tried during at least 2 hours). Can anyone help me?
Many thanks
> ccrit <- 0 
> cmax <- 5 
> cclass <- ccrit:cmax 
> nc <- length(cclass) 
> tmax <- 10 
> times <- 1:(tmax-1)
> nprey <- 3
> dive <- c(0.02,0.1,0.14)
> pfood <- c(200,60,40)
> f <- matrix(nrow=cmax,ncol=nc ,0) 
> bestpatch <- matrix(nrow=tmax-1,ncol=nc-1,0)
> V <- vector(length=nprey)
> fitness <- function(c,t)
+ {
+ cc <- pmin(c ,cmax)
+ cc <- pmax(cc,ccrit)
+ fitness <- f[t,cc-ccrit+1]
+ }
> for (t in rev(times))
+ {
+ for (c in cclass[-1])
+ {
+ V<-fitness*(c+dive*pfood, t+1)
Error: unexpected ',' in:
"{
V<-fitness*(c+dive*pfood,"
> f[t,c-ccrit] <- max(V)
Error in c - ccrit : non-numeric argument to binary
operator
> bestpatch[t,c-ccrit+1] <- which.max(V)
Error in c - ccrit : non-numeric argument to binary
operator
> }
Error: unexpected '}' in "}"
> }
Error: unexpected '}' in "}"
> 

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On 05/29/2011 06:07 AM, garciap wrote:
> V<-fitness*(c+dive*pfood, t+1)
What are you trying to do in this line?  Multiply fitness by two 
different things at once?  The expression

(1,2)

Causes problems in R.  If you want to combine them into a vector, you need

c(1,2)

Otherwise, please go into greater detail about what you are trying to 
accomplish with this line of code.

Also, probably not a good idea to have a variable called 'c', as this is
bound to lead to confusion with the function for combining objects,
'c()'.

-- 
Patrick Breheny
Assistant Professor
Department of Biostatistics
Department of Statistics
University of Kentucky