View source: R/ddfilter_loop.R
ddfilter_loop | R Documentation |
A partial component of ddfilter
, although works as a stand-alone function.
This function removes locations by speed, inner angle, and quality index as described in Shimada et al. (2012).
ddfilter_loop(sdata, qi = 4, ia = 90, vmaxlp = 1.8)
sdata |
A data frame containing columns with the following headers: "id", "DateTime", "lat", "lon", "qi".
See the data |
qi |
An integer specifying a threshold of quality index, which is used to evaluate the locations of loop trips. Default is 4. |
ia |
An integer specifying a threshold of inner angle, which is used to evaluate the locations of loop trips. Default is 90 degrees. |
vmaxlp |
A numeric value specifying a threshold of speed, which is used to evaluate the locations of loop trips.
Default is 1.8 km/h.
If this value is unknown, it can be estimated from sdata using the function |
This function removes locations if all of the following criteria apply:
the number of source satellites are less than or equal to qi,
the inner angle is less than and equal to ia and the speed either from a previous or to a subsequent location exceeds vmaxlp.
If vmaxlp is unknown, it can be estimated using the function vmaxlp
.
The input data is returned without locations identified by this filter. The following columns are added: "pTime", "sTime", "pDist", "sDist", "pSpeed", "sSpeed", "inAng". "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. "pSpeed" and "sSpeed" are linear speed from a previous and to a subsequent fix respectively. "inAng" is the degree between the bearings of lines joining successive location points.
Takahiro Shimada
Shimada T, Jones R, Limpus C, Hamann M (2012) Improving data retention and home range estimates by data-driven screening. Marine Ecology Progress Series 457:171-180 \Sexpr[results=rd]{tools:::Rd_expr_doi("10.3354/meps09747")}
ddfilter
, ddfilter_speed
, vmaxlp
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