Description Usage Arguments Details Value
Simulate a new track from the parameters of a fitted rwalc
model.
1 2 3 4 5 6 7 8 |
data |
A dataframe representing the template track. |
par |
The model parameters. |
fixed |
An integer vector indicating which locations in the template path are to be held fixed. |
fixed.err |
Covariance matrix for fixed points. |
point.check |
A function that accepts a time, and an x,y location and returns a logical indicating whether the location is acceptable. |
point.accept |
A logical vector indicating which locations
should not be checked with the |
Given a template track and the parameters of a rwalc model this function generates a new track of the same length that coincides with the fitted track at the start point and optionally other specified points along the template track.
Locations from the template track can be marked as fixed with the
fixed
argument. This should either be NULL
or a
vector with an entry for each location, with entries indicating
0 the location is not fixed
1 the location is fixed
2 the location is fixed and the point may be a cusp (autocorrelation is reset).
In the current implementation the first location in each segment
must be fixed. The fixed.err
parameter specifies the
covariance of the error in the fixed points, allowing the user to
control how acccurately the simulated track reproduces the four
components (locations and velocities) of the fixed points.
Additional constraints can be placed on the path by rejection
sampling through the function point.check
. This function
must accept a time, x and y and return a logical indicating
whether the point is acceptable. For example, the track can be
constrained to the ocean by supplying a point.check
function that compares the state to a land mask and returns
FALSE
for locations on land.
The point.accept
can be used to mark points that should not
be checked in the rejection step. Currently this defaults to the
value of fixed
- so by default fixed points are never
checked.
Tracks are simulated in the plane. There is is no polar
correction and without a suitable point.check
function,
there is nothing prevent the track extending outside the [-90,90]
latitudinal limits.
Returns a dataframe representing the simulated track with columns
segment |
track segment |
date |
time (as GMT POSIXct) |
x |
x coordinate |
y |
y coordinate |
x.v |
x component of velocity |
y.v |
y component of velocity |
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