SDLfilter (version 1.2.1)

dupfilter: Filter temporal and/or spatial duplicates

Description

Function to remove temporal and/or spatial duplicates.

Usage

dupfilter(sdata, step.time = 0, step.dist = 0, conditional = FALSE)

Arguments

sdata

A data frame containing columns with the following headers: "id", "DateTime", "lat", "lon", "qi". This filter is independently applied to a subset of data grouped by the unique "id". "DateTime" is date & time in class POSIXct. "lat" and "lon" are the recorded latitude and longitude in decimal degrees. "qi" is the numerical quality index associated with each fix where the greater number represents better quality (e.g. number of GPS satellites used for estimation).

step.time

A numeric value specifying temporal interval between two consecutive locations. Default is 0 hours. Locations are considered temporal duplicates if the temporal interval is less than or equal to the user specified value.

step.dist

A numeric value specifying spatial interval between two consecutive locations. Default is 0 kilometres. Locations are considered spatial duplicates if the spatial interval is less than or equal to the user specified value.

conditional

If TRUE, spatial duplicates are removed only if temporal interval between the locations is less than the time specified in "step.time". Default is FALSE.

Value

Input data frame is returned with spatial and 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.

Details

A fix associated with a higher quality index is retained over other duplicated fixes. If temporal duplicates are associated with same quality index, a fix located closest to a previous and a subsequent location is retained.

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

See Also

dupfilter.exact, dupfilter.qi, dupfilter.time, dupfilter.space

Examples

# NOT RUN {
#### Load data sets
## Fastloc GPS data obtained from a green turtle
data(turtle)


#### Apply dupfilter
turtle.dup <- dupfilter(turtle)
# }