I would like to create a ggplot2 plot by faceting geom_function, so that a parameter of the function varies across the grid. e.g. something like this:

my_function<-function(x, par)
{
 if(par==1)
 {
  return(sin(x))
 }
 else
 {
  return(cos(x))
 }
}

> head(data)
      x parameter
1 -1.00   1
2 -0.99   1
3 -0.98   1
4 -0.97   1
5 -0.96   1
6 -0.95   1

> tail(data)
       x parameter
397 0.95   2
398 0.96   2
399 0.97   2
400 0.98   2
401 0.99   2
402 1.00   2

> my_plot<-ggplot(data, aes(x)) + geom_function(fun = my_function, args=list(par=parameter)+facet_wrap(~parameter)

which doesn't work because "parameter" is not in scope for the args parameter of geom_function. Is this possible?