with.ssf:
Evaluate Expression in a Spatially Sampled Function
Description
Given a spatially sampled function,
evaluate an expression involving the function values.
Usage
apply.ssf(X, ...)
"with"(data, ...)
Arguments
X, data
A spatially sampled function (object of class "ssf").
...
Arguments passed to with.default or
apply specifying what to compute.
Value
An object of class "ssf" or a numeric vector.
Details
An object of class "ssf" represents a
function (real- or vector-valued) that has been
sampled at a finite set of points.
It contains a data frame
which provides the function values
at the sample points.
In with.ssf, the expression specified by ...
will be evaluated in this dataframe.
In apply.ssf, the dataframe will be subjected to
the apply operator using the additional arguments
....
If the result of evaluation
is a data frame with one row for each data point,
or a numeric vector with one entry for each data point,
then the result will be an object of class "ssf"
containing this information. Otherwise, the result will be
a numeric vector.