vmax | R Documentation |
Function to estimate the maximum linear speed between two consecutive locations.
vmax(sdata, qi = 5, method = "ML", prob = 0.99, ...)
sdata |
A data frame containing columns with the following headers: "id", "DateTime", "lat", "lon", "qi".
See the data |
qi |
An integer specifying the lowest quality index of a location that is qualified to be used in the estimation. Default is 5 (e.g. 5 GPS satellite or more). |
method |
Available options are "sample" (i.e. sample quantile - see |
prob |
A value (0 to 1) specifying the sample quantile or cumulative probability for linear speed. Values beyond this threshold are considered 'outliers' and excluded from estimation of maximum linear speed. Default is 0.99. See details. |
... |
Extra arguments passed to |
The function first calculates the linear speed between each pair of two consecutive locations.
Some of the calculated linear speed can be inaccurate when the input data contains inaccurate locations (e.g. outliers).
The function can discard the implausible outliers by excluding extreme values using either the "sample" or "ML" method.
The "sample" method simply discards values that lie beyond the specified quantile.
If the "ML" method is selected, it is assumed that the linear speed follow a Gamma distribution.
The distribution parameters are derived via maximum likelihood estimation using the optim
function.
The linear speed at the given quantile or cumulative probability (e.g. 0.99) represents the maximum linear speed at which
an animal would travel between two consecutive locations.
Maximum linear speed (vmax) estimated from the input data. The unit is km/h.
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
, track_param
, dupfilter
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