R/filter_data_time_interval.R

In Nature40/UM2Radiotracking: Toolkit for handling radiotracking data

#' Filter data with time interval
#'
#' @description Filter radiotracking data with start and end time
#'
#' @param data data.frame of radiotrackin data
#' @param time_distance vector with two POSIXct times
#'
#' @return data.frame of filtered radiotracking data
#'
#' @author RadioTracking EU
#'
#' @export


filter_data_time_interval <- function(data,time_distance){
  #find for each receiver
  list_of_receivers<-unique(data$receiver)
  #and each frequency
  list_of_frequencies<-unique(data$freq_tag)
  #signals which appear betweeen time_distance[1] and time_distance[2] seconds
  return_tmp<-NULL
  for(i in list_of_receivers){
    tmp1 <- subset(data,receiver==i)
    for(k in list_of_frequencies){
      tmp2<-subset(tmp1,freq_tag==k)
      tmp2<-tmp2[order(tmp2$timestamp),]
      #calcualte the time distance between the impulses
      if(nrow(tmp2)>1){
        td<-diff(tmp2$timestamp)
        if(attr(td,"units")=="secs"){
          td<-c(td,td[length(td)])
          tmp2<-cbind(tmp2,td=td)
          test<-tmp2$td>time_distance[1]&tmp2$td<time_distance[2]
          i<-1
          while(i<length(test)-1){
            if(!test[i+1]&&test[i]){
              test[i+1]<-TRUE
              i<-i+1
            }
            i<-i+1
          }
          tmp2<-tmp2[test,]
          return_tmp<-rbind(tmp2,return_tmp)
        }
      }
    }
  }
  return(return_tmp)
}