ddfilter_speed | R Documentation |
A partial component of ddfilter
, although works as a stand-alone function.
This function removes locations by a given threshold speed as described in Shimada et al. (2012).
ddfilter_speed(sdata, vmax = 8.9, method = 1)
sdata |
A data frame containing columns with the following headers: "id", "DateTime", "lat", "lon", "qi".
See the data |
vmax |
A numeric value specifying a threshold of speed from a previous and/or to a subsequent fix.
Default is 8.9km/h.
If this value is unknown, it can be estimated from sdata using the function |
method |
An integer (1 or 2) specifying how locations should be filtered. Default is 1 and removes a location if the speed from a previous AND to a subsequent location exceeds vmax. Select 2 to remove a location if the speed from a previous OR to a subsequent location exceeds vmax. For the latter, the filter examines successive suspect locations (i.e. the speed from a previous and/or to a subsequent location exceeds vmax) and retain one location that is associated with the minimum speed from a previous and to a subsequent location. |
This function removes locations if the speed from a previous and/or to a subsequent location exceeds a given threshold speed.
If vmax is unknown, it can be estimated using the function vmax
.
The input data is returned without locations identified by this filter. The following columns are added: "pTime", "sTime", "pDist", "sDist", "pSpeed", "sSpeed". "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.
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_loop
, vmax
, track_param
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