| invoke.metric {spatstat.geom} | R Documentation |
Perform Geometric Task using a Specified Metric
Description
Perform a desired geometrical operation using a specified distance metric.
Usage
invoke.metric(m, task, ..., evaluate=TRUE)
Arguments
m |
Metric (object of class |
task |
Character string specifying the task. The name of a function that performs the desired operation for the Euclidean metric. |
... |
Input to the function that performs the geometrical operation
(matching the arguments of |
evaluate |
Logical value specifying whether to actually perform the
computation and return the result ( |
Details
A ‘metric’ is a measure of distance between points in space.
An object of class "metric" represents such a metric,
and supports many geometrical computations that involve
the metric. See metric.object.
The argument task should be the name of an existing function
in the spatstat family representing a geometrical operation, such
as computing pairwise distances, nearest-neighbour distances,
the distance map, and so on. The code will determine whether
this geometrical operation has a counterpart using the specified metric,
that is defined and supported in the object m.
If so, then this operation will be applied to the
data specified in ..., and the result will be returned.
For example, the spatstat function nndist.ppp computes
nearest-neighbour distances using the Euclidean distance metric.
To calculate nearest-neighbour distances for a point pattern X
using another metric m,
use invoke.metric(m, "nndist.ppp", X).
If evaluate=FALSE, the computation is not performed,
and invoke.metric simply returns a function to
perform the desired operation.
Value
If evaluate=TRUE (the default), the result of the computation has the
same format as the result of the computation using the existing
function named task.
If evaluate=FALSE, the result is a function in the R language
to perform the desired operation;
or NULL if the operation is not supported by the metric.
Author(s)
Adrian Baddeley Adrian.Baddeley@curtin.edu.au.
See Also
Examples
## nearest-neighbour distances using rectangular metric (L^1 metric)
d <- convexmetric(square(c(-1,1)))
y <- invoke.metric(d, "nndist.ppp", cells)
f <- invoke.metric(d, "nndist.ppp", cells, evaluate=FALSE)
y <- f(cells)
invoke.metric(d, "orderPizza", evaluate=FALSE)