Applies independent random displacements to each point in a three-dimensional point pattern.
# S3 method for pp3
rjitter(X, radius, retry=TRUE, giveup = 10000, trim=FALSE,
..., nsim=1, drop=TRUE, adjust=1)The result of rjitter.pp3 is
a three-dimensional point pattern (an object of class "pp3")
or a list of 3D point patterns.
Each point pattern has attributes "radius"
and (if retry=TRUE) "tries".
A point pattern (object of class "ppp").
Scale of perturbations. A positive numerical value.
The displacement vectors will be uniformly
distributed inside a sphere of this radius.
There is a sensible default.
Alternatively, radius may be a numeric vector of length
equal to the number of points in X, giving a different
displacement radius for each data point.
What to do when a perturbed point lies outside the window
of the original point pattern. If retry=FALSE,
the point will be lost; if retry=TRUE,
the algorithm will try again.
Maximum number of unsuccessful attempts.
Logical value. If TRUE, the displacement radius
for each data point will be constrained to be less than or equal to
the distance from the data point to the window boundary.
This ensures that all displaced points will fall inside the window.
Ignored.
Number of simulated realisations to be generated.
Logical. If nsim=1 and drop=TRUE (the default), the
result will be a point pattern, rather than a list
containing a point pattern.
Adjustment factor applied to the radius. A numeric value or numeric vector.
Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner rolfturner@posteo.net and Ege Rubak rubak@math.aau.dk.
The function rjitter is generic, with methods for point
patterns and for some other types of geometrical objects.
This help page describes the method for three-dimensional point
patterns of class "pp3".
Each of the points in the point pattern X is subjected to
an independent random displacement. The displacement vectors are
uniformly distributed in a sphere of radius radius.
If a displaced point lies outside the domain of the pattern, then if
retry=FALSE the point will be lost.
However if retry=TRUE, the algorithm will try again: each time a
perturbed point lies outside the domain, the algorithm will reject
the perturbed point and
generate another proposed perturbation of the original point,
until one lies inside the domain, or until giveup unsuccessful
attempts have been made. In the latter case, any unresolved points
will be included, without any perturbation. The return value will
always be a point pattern with the same number of points as X.
If trim=TRUE, then the displacement radius for each data point
will be constrained to be less than or equal to
the distance from the data point to the domain boundary.
This ensures that the randomly displaced points will
always fall inside the domain; no displaced points will be lost and no
retrying will be required. However, it implies that a point lying
exactly on the boundary will never be perturbed.
If adjust is given, the jittering radius will be multiplied
by adjust. This allows the user to specify
that the radius should be a multiple of the default radius.
The resulting point pattern
has an attribute "radius" giving the value
of radius used.
If retry=TRUE, the resulting point pattern also has an attribute
"tries" reporting the maximum number of trials needed to
ensure that all jittered points were inside the domain.
rjitter
X <- osteo$pts[[1]]
Y <- rjitter(X, 5)
plot(Y)
Z <- rjitter(X)
U <- rjitter(X, 5, trim=TRUE)
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