R/optme.R

In filBe87/PKUss: Helper functions for species distribution modelling practicals of the Peking Unversity summer school 2019

### =========================================================================
### optimization function for cluster distribution
### =========================================================================
#' Optimization function to create equal-sized strata in the 'make_blocks' function
#'
#' Not to be called directly by the user
#' @author Philipp
#' @export
optme=function(x,nms,grps,tot){

  # determine number of bservations in each groups from initial step
  grp=sapply(grps,"sum")

  # aggregate remaining observations by suggested cluster grouping
  x=as.numeric(as.character(x))
  agg.vals=aggregate(nms,by=list(x),FUN="sum")

  for(i in 1:length(grp)){

    if(i%in%agg.vals$Group.1){
      grp[i]=agg.vals$x[which(agg.vals$Group.1==i)]+grp[i]
    }

  }

  # Calculate difference from equal distribution
  pen=(grp-tot/length(grp))^2

  return(sum(pen))

}