sub_sampling_by_dist_nb_stat <- function(target_range_nb,dist_range,step_dist,data_in,sampling=T,combined=F){

  ##This functions perform subsampling for tiles/region wiht a high density of region.

  ##Sub-sampling can be done through spatial pruning by providing  a range of distance and step or

  ##by using random sampling in addition  to spatial pruning.

  #Input parameters:

  #sampling: if  TRUE use random sampling  in addition to spatial  sub-sampling

  #target_range_nb : number of stations desired as min and max, convergence to  min  for  now

  #dist_range : spatial distance range  for pruning,  usually (0,5) in km or 0,0.009*5 for  degreee

  #step_dist : stepping distance used in pruning  spatially, use 1km or 0.009 for degree data

  #data_in : input data to be resampled (data.frame or spatial point df.)

  #combined: if FALSE, combined, add variable to  show wich  data rows  were removed (not currently in use)

  #

  #Output parameters:

  #data: subsampled data

  #dist: distance at which spatial sub-sampling  ended

  #data_removed: data that was removed from the input data frame

  #data_dist: data item/stations after using spatial pruning, only appears if sampling = T

  #### START PROGRAM BODY #####

#dist_range <- c(0,10000) 

target_range_nb <- c(target_min_nb,target_max_nb) #target range of number of stations

step_dist <- 1000 #iteration step to remove the stations, 1000 meters

#test4 <- sub_sampling_by_dist_nb_stat(target_range_nb=c(100,200),dist_range=c(0,10000),data_in=data_month,sampling=T,combined=F)

test4 <- sub_sampling_by_dist_nb_stat(target_range_nb=c(100,200),dist_range=c(0,10000),step_dist=step_dist,data_in=data_month,sampling=T,combined=F)

### for NEX, most likely settings:

target_max_nb <- 100,000 #this is not actually used yet in the current implementation,can be set to very high value...

target_min_nb <- 8,000 #this is the target number of stations we would like: to be set by Alberto...

#max_dist <- 1000 # the maximum distance used for pruning ie removes stations that are closer than 1000m, this in degree...? 

max_idst <- 0.009*5 #5km in degree

min_dist <- 0    #minimum distance to start with

step_dist <- 0.009 #iteration step to remove the stations

test5 <- sub_sampling_by_dist_nb_stat(target_range_nb=target_range_nb,dist_range=dist_range,step_dist=step_dist,data_in=data_month,sampling=T,combined=F)