code

geo_tweet<-function(lat,long,radius,data,date1,date2){
  #Data is assumed to have the form reported in the search tweet API vs
  #where the column geo.geo.coordinates contains exact geolocation:
  
  if(date1>date2){
    stop("Initial date and final date are not correct")
  }
  #transform as dates:
  
  data$created_at<- strptime(data$created_at, "%Y-%m-%d %H:%M:%S")
  
  #1) Divide in two columns for latitude and longitude:
  
  data$geo.coordinates.coordinates<-gsub("\\[|\\]", "", 
                                            data$geo.coordinates.coordinates)
  
  foo<-data.frame(do.call('rbind', 
                          strsplit(as.character(data$geo.coordinates.coordinates),
                                   ',',fixed=TRUE)))
  
  # two new columns added for the coordinates (named lng and lat by default)
  data$lng<-as.numeric(foo$X1)
  data$lat<-as.numeric(foo$X2)  
  
  #2) Select the radius around the point:
  

  data$distance<-(geosphere::distHaversine(cbind("longitude"=data$lng,
                                                    "latitude"=data$lat), 
                                              c(long,lat)))/1000<radius 
  #this adds a column distance of logicals to compare distances
  
  #3) Filter by specific date:
  
  
  date_subset<<-subset(data,eval(
                      data$created_at>=as.POSIXct(date1)&
                        data$created_at<=as.POSIXct(date2)))
   date_subset

    return(data)
  # return(date_subset)
}