R/logistic.R

In flr/FLife: Methods for Modelling Life History Traits

#' logistic
#'
#' logistic function
#' 
#' @param params \code{FLPar} with parameters a50,ato95 and asym
#' @param age \code{FLQuant} with ages
#' @param ... other arguments
#' 
#' @export
#' @docType methods
#' @rdname logistic
#' 
#' @aliases logistic logistic-method logistic,FLQuant,FLPar-method
#' 
#' @seealso \code{\link{gompertz}}
#' 
#' @examples
#' \dontrun{
#' params=FLPar(a50=4,ato95=1,asym=1.0)
#' age=FLQuant(1:10,dimnames=list(age=1:10))
#' logistic(age,params)
#' }
setMethod('logistic', signature(age='FLQuant',params='FLPar'),
          function(age,params,...) { 
            res=logisticFn(age,params)
            res@units='proportion'
            res})

logisticFn<-function(age,params) { #x,a50,ato95,asym=1.0){  
  
  res =params["asym"]%/%(1.0+pow(19.0,(params["a50"]%-%age)%/%params["ato95"]))
  res[is.na(res)]=0
  asym=FLQuant(1,dimnames=dimnames(age))%*%params["asym"]
  grt =(params["a50"]%-%age)%/%params["ato95"] >  5
  lss =(params["a50"]%-%age)%/%params["ato95"] < -5
  
  res[grt]=0
  res@.Data[lss]=asym@.Data[lss]
  
  dmns          =dimnames(res)
  names(dmns)[1]="age"
  dimnames(res) =dmns
  
  return(res)}