R: Filter temporal duplicates

dupfilter_time {SDLfilter}

R Documentation

Filter temporal duplicates

Description

Function to filter temporal duplicates that are associated with the same quality index.

Usage

dupfilter_time(sdata, step.time = 0, no.cores = 1)

Arguments

`sdata`	A data frame containing columns with the following headers: "id", "DateTime", "lat", "lon", "qi". See the data `turtle` for an example. The function filters the input data by a unique "id" (e.g. transmitter number, identifier for each animal). "DateTime" is the GMT date & time of each location in class `POSIXct` or `character` with the following format "2012-06-03 01:33:46". "lat" and "lon" are the latitude and longitude of each location in decimal degrees. "qi" is the quality index associated with each location fix. The input values can be either the number of GPS satellites or Argos Location Classes. Argos Location Classes will be converted to numerical values, where "A", "B", "Z" will be replaced with "-1", "-2", "-3" respectively. The greater number indicates a higher accuracy.
`step.time`	Consecutive locations less than or equal to step.time apart are considered temporal duplicates. Default is 0 hours.
`no.cores`	An integer specifying the number of cores used for parallel computing. Alternatively, type in 'detect' to use the maximum number of available cores minus one.

Details

This is a partial component of dupfilter, although works as a stand-alone function. First it identifies temporal duplicates by searching for consecutive locations that were obtained within step.time. For each group of temporal duplicates, the function then retains a single fix that is nearest from a previous and to a subsequent location.

Value

The input data frame is returned with temporal duplicates removed. The following columns are added: "pTime", "sTime", "pDist", "sDist". "pTime" and "sTime" are hours from a previous and to a subsequent fix respectively. "pDist" and "sDist" are straight distances in kilometres from a previous and to a subsequent fix respectively.

Author(s)

Takahiro Shimada

References

Shimada T, Limpus C, Jones R, Hazel J, Groom R, Hamann M (2016) Sea turtles return home after intentional displacement from coastal foraging areas. Marine Biology 163:1-14 doi:10.1007/s00227-015-2771-0