R/uniroot.all.R

In Trinity-Automata-Research/dsmodels: A Language to Facilitate Simulation and Visualization of Two-Dimensional Dynamical Systems

# This file was originally written by Karline Soetaert for the rootSolve package under the GPL 2. This version, modified by Nicholas Smoker, is here used by dsmodels under the terms of the GPL 2 (which dsmodels also uses).

## =============================================================================
## uniroot.all: multiple roots of one nonlinear equation
## =============================================================================

uniroot.all <- function (f, interval, lower= min(interval),
        upper= max(interval), tol= .Machine$double.eps^0.25,
        maxiter= 1000, n = 100, ... ) {

## error checking as in uniroot...
  if(!missing(interval) && length(interval) != 2)
     stop("'interval' must be a vector of length 2")
  if(!is.numeric(lower) || !is.numeric(upper) || lower >= upper)
    stop("lower < upper  is not fulfilled")

## subdivide interval in n subintervals and estimate the function values
  xseq <- seq(lower,upper,len=n+1)
  mod  <- f(xseq,...)

## some function values may already be 0
  Equi <- xseq[which(mod==0)]

  ss   <- mod[1:n]*mod[2:(n+1)]  # interval where functionvalues change sign
  ii   <- which(ss<0)

  for (i in ii)
    Equi <- c(Equi,uniroot(f,lower=xseq[i],upper=xseq[i+1], tol = tol, ...)$root)

  return(Equi)
}