min_lag: Calculate 'min_lag' for identifying potential false positive...

In jsta/glatos: A package for the Great Lakes Acoustic Telemetry Observation System

Calculate 'min_lag' for identifying potential false positive detections

Description

Calculate minimum time interval (min_lag) between successive detections and add to detection data set for identifying potential false detections.

Usage

min_lag(det)

Arguments

det

A glatos_detections object (e.g., produced by read_glatos_detections). OR a data frame containing detection data with the following columns: detection_timestamp_utc Detection timestamps; MUST be of class POSIXct. transmitter_codespace A character string with transmitter code space (e.g., "A69-1061" for Vemco PPM coding"). transmitter_id A character string with transmitter ID code (e.g., "1363" for Vemco PPM coding"). receiver_sn A character vector with unique receiver serial number.

Details

min_lag is loosely based on the the "short interval" described by Pincock (2012) and replicates the min_lag column in the standard glatos detection export file. In this case (GLATOS), min_lag is defined for each detection as the shortest interval (in seconds) between either the previous or next detection (whichever is closest) of the same transmitter code (defined here as combination of transmitter_codespace and transmitter_id) on the same receiver.

A new column (min_lag) is added to the input dataframe that represents the time (in seconds) between the current detection and the next detection (either before or after) of the same transmitter on the same receiver. This function replicates the 'min_lag' column included in the standard glatos export.

Value

A column min_lag (defined above) is added to input object.

Author(s)

Chris Holbrook, Todd Hayden, Angela Dini

References

Pincock, D.G., 2012. False detections: what they are and how to remove them from detection data. Vemco Division, Amirix Systems Inc., Halifax, Nova Scotia.
http://www.vemco.com/pdf/false_detections.pdf

See Also

false_detections

Examples

# load example detection file
det_file <- system.file("extdata", "walleye_detections.csv",
                         package = "glatos")
det <- read_glatos_detections(det_file)

# rename existing min_lag column
colnames(det)[colnames(det) == "min_lag"] <- "min_lag.x"

# calculate min_lag
det <- min_lag(det)

head(det)

jsta/glatos documentation built on July 11, 2022, 7:01 a.m.