prefilter {telemetR}

Apply the "prefilter" to a Detection Dataframe

Description

This function takes a detection dataframe output from format_detects and filters out multipath signals (signals which are bounced off of surfaces, usually seen in underwater systems with hard surfaces which reflect sound) and spurious signals which do not occur within a user defined time frame of the last detection (12x the ping rate for organisms or 3x the ping rate for beacons). Following this, the dataframe is standardized so that all detection dataframes from any technology type are identical and superfluous fields are removed.

Usage

prefilter(
  data,
  reference_tags,
  time_unit,
  multipath_time,
  org_ping_rate,
  beacon_ping
)

Arguments

data

A dataframe which is the output from read_jstats() or format_detects()

reference_tags

A vector of potential reference (beacon) tag IDs

time_unit

The unit of time used for analyses (seconds, minutes, hours, days, weeks, months)

multipath_time

A numeric maximum amount of time which must pass between detections for a detection to be considered a "true", not a bounced, signal.

org_ping_rate

The expected time between transmissions emitted from tags/transmitters implanted or attached to an organism

beacon_ping

The expected time between transmissions emitted from tags/transmitters used as beacon or reference tags to check receiver functionality.

Value

A standardized detection dataframe with multipath detects removed

Examples

# Run the prefilter on a set of raw detection data

#format the detection data
detects_formatted <- format_detects(data = raw_detections,
                                    var_Id = "tag_id",
                                    var_datetime_local = "local_time",
                                    var_receiver_serial = "serial",
                                    local_time_zone = "America/Los_Angeles",
                                    time_format = "%Y-%m-%d %H:%M:%S")

#apply the prefilter
prefilter(data = detects_formatted,
          reference_tags = reftags,
          time_unit = "secs",
          multipath_time = 0.3,
          org_ping_rate = 3,
          beacon_ping = 30)