[R] A Hodgkin Huxley Model

David Winsemius dwinsemius at comcast.net
Mon Feb 11 01:09:35 CET 2013

```On Feb 10, 2013, at 3:35 PM, Jannetta Steyn wrote:

> I managed to get it to work (I think). Code below:
>

The output certainly looks more sensible. You commented out the if-
reset strategy and are using events. Can you explain how the event
code is triggered? I no longer see a definition of a v>=30 trigger.
The vignette says "Events occur when the values of state variables are
instantaneously changed. They can be specified as a data.frame, or in
a function. Events can also be triggered by a root function." Is the
code detecting the sudden rise to infinite values and using that as
the trigger for a reset?

--
David.

> library(deSolve);
> Izhikevich <- function(time, init, parms) {
>  with(as.list(c(init, parms)),{
>    dv <- (0.04*v^2)+(5*v)+140-u+I;
>    du <- a*(b*v-u);
>    #if (v>=30) v<-c else v<-u+d;
>    list( c(dv, du))
>  })}
> parms=c( a=0.02, b=0.2, c=-65, d=2, I=4);
> times=seq(from=1, to=500, by=0.1);
> init=c(v=-65, u=0.2);
>
> root <- function(time, init, parms) init[1]
>
> event <- function(time, init, parms) {
>  with(as.list(c(init, parms)), {
>  init[2] <- init[1] + d
>  init[1] <- c
>  return(init)
>  })
> }
>
> out<-ode(y=init, times=times, func=Izhikevich, parms=parms,
> events=list(func=event, root=TRUE), rootfun=root)
> plot(out)
>
>
> Thanks everybody for their help.
>
> Jannetta
>
> 	[[alternative HTML version deleted]]
>
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