Error originates in the customized function ode. When IN!=0, You did
not assign a value to dIN which is required in list(c(dP1,dP2,dIN)).
On 2010-9-21 2:30, Tianchan Niu wrote:
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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