[R] ERROR: Object not found

Tianchan Niu
2010-09-20T18:30:30Z

Dear All,



I am trying to use ode solver "rk4" to solve an ODE system, however,
it
keeps saying: Error in eval(expr, envir, enclos) : object "dIN" not
found.
The sample codes are enclosed as follows, please help me. Thank you very
much!



rm(list=ls())



library(odesolve)



# The ODE system

ode <- function(t,x,p){



  with(as.list(c(x,p)),{



     if(IN==0){

       dIN <- 1

       switch <- c

     }

     else {

       switch <- 0

     }



     dP1 <- a+b*P1-switch*P1

     dP2 <- a-b*P1+switch*P2



  list(c(dP1,dP2,dIN))

  })

}



# Parameters

a <- 0.1

b <- 0.2

c <- 0.5



parms <- c(a=a,b=b,c=c)



# Initial conditions

P10 <- 100.0

P20 <- 0.0

IN0 <- 0.0



xstart <- c(P1=P10,P2=P20,IN=IN0)



# Time points

times <- seq(0,10,by=1)



out <- as.data.frame(rk4(xstart,times,ode,parms))


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