R/ex_vdpol.R

In deTestSet: Test Set for Differential Equations

## =============================================================================
##
## van der Pol problem
##
## This code is derived from the Test Set for IVP solvers
##     http://www.dm.uniba.it/~testset/
##     ODE of dimension 2
##
## =============================================================================

vdpol <- function(times = 0:2000, yini = NULL, parms = list(), 
		              printmescd = TRUE, atol = 1e-6, rtol = 1e-6, ...) {

### derivative function
  Vdpol <- function(t,y,mu) {
    list(c(
    y[2],
    mu * (1 - y[1]^2) * y[2] - y[1]
  ))
}

### check input 
    parameter <- c(mu = 1000)

    parameter <- overrulepar(parameter, parms, 1)

    if (is.null(yini))  yini <- c(y1 = 2, y2 = 0) 
    checkini(2, yini)
	prob <- vdpolprob()

### solve
    out <- ode(func = Vdpol, parms = parameter, y = yini, times = times,
			atol=atol,rtol=rtol, ...)
   if(printmescd) 
     out <- printpr (out, prob, "vdpol", rtol, atol)	
   return(out)
}




vdpolprob <- function(){ 
	fullnm <- 'Problem VANDERPOL'
	problm <- 'vdpolm'
	type   <- 'ODE'
	neqn   <- 2
	t <- matrix(1,2)
	t[1]   <- 0
	t[2]   <- 2000
	numjac <- TRUE
	mljac  <- neqn
	mujac  <- neqn	
	return(list(fullnm=fullnm, problm=problm,type=type,neqn=neqn,
					t=t,numjac=numjac,mljac=mljac,mujac=mujac))
}