R/centroid.R

In Nature40/UM2Radiotracking: Toolkit for handling radiotracking data

#' Centroid triangulation over time
#' @description Smooth triangulation points with centroids
#'
#' @param tri_data data.frame. triangulated points
#' @param time numeric. time in minutes to aggregate triangulation points
#' @param s_time numeric. time in second. How much points in each minute
#' @param method string. either mean or median
#'
#' @return smoothed triangulations
#'
#' @author RadioTracking EU
#'
#' @import foreach
#'
#' @export

centroid <- function(tri_data, time, s_time, method="mean"){
  min_time <- min(tri_data$timestamp)
  max_time <- max(tri_data$timestamp)
  time_seq <- seq(round(min_time, "mins") - 60, round(max_time, "mins") + 60, by = 60*time)
  utm <- foreach::foreach(i = time_seq,
                          .combine = rbind,
                          .inorder = F) %dopar% {
                            tmp <- subset(tri_data,timestamp>=i&timestamp<i+60*s_time)
                            zone<-(floor((tmp$pos.X[1] + 180)/6) %% 60) + 1
                            if(nrow(tmp)>0){
                              data.frame(timestamp=i,
                                         freq_tag=tmp$freq_tag[1],
                                         pos.utm.X=switch(method,
                                                          mean=mean(tmp$pos.utm.X),
                                                          median=median(tmp$pos.utm.X)),
                                         pos.utm.Y=switch(method,
                                                          mean=mean(tmp$pos.utm.Y),
                                                          median=median(tmp$pos.utm.Y)),
                                         utm.zone=zone)
                            }

               }
  location_wgs<-utmtowgs(utm$pos.utm.X,utm$pos.utm.Y,utm$utm.zone)
  return(cbind(utm,pos=location_wgs))
}