Evaluate an Expression in a Function Table
Evaluate an R expression in a
function value table (object of class "fv").
## S3 method for class 'fv' with(data, expr, ..., fun = NULL, enclos=NULL)
data |
A function value table (object of class |
expr |
The expression to be evaluated. An R language
expression, which may involve the names of columns in |
... |
Ignored. |
fun |
Logical value, specifying whether the result
should be interpreted as another function ( |
enclos |
An environment in which to search for variables that are
not found in |
This is a method for the generic command with
for an object of class "fv" (function value table).
An object of class "fv" is a convenient way of storing and
plotting several different estimates of the same function. It is
effectively a data frame with extra attributes.
See fv.object for further explanation.
This command makes it possible to perform computations that involve different estimates of the same function. For example we use it to compute the arithmetic difference between two different edge-corrected estimates of the K function of a point pattern.
The argument expr should be an R language expression. The expression
may involve
the name of any column in data, referring to
one of the estimates of the function;
the symbol . which stands for all
the available estimates of the function;
the symbol .y which stands for the recommended
estimate of the function (in an "fv" object, one of the
estimates is always identified as the recommended estimate);
the symbol .x which stands for the argument of the function;
global constants or functions.
See the Examples. The expression should be capable of handling vectors and matrices.
The interpretation of the argument fun is as follows:
If fun=FALSE, the result of evaluating the expression
expr will be returned as a numeric vector, matrix or
data frame.
If fun=TRUE, then the result of evaluating expr
will be interpreted as containing the values of a new function.
The return value will be an object of class "fv".
(This can only happen if the result has the right dimensions.)
The default is fun=TRUE if the result of evaluating
expr has more than one column, and fun=FALSE otherwise.
To perform calculations involving several objects of
class "fv", use eval.fv.
A function value table (object of class "fv")
or a numeric vector or data frame.
Adrian Baddeley Adrian.Baddeley@curtin.edu.au
and Rolf Turner r.turner@auckland.ac.nz
# compute 4 estimates of the K function X <- runifrect(42) K <- Kest(X) plot(K) # derive 4 estimates of the L function L(r) = sqrt(K(r)/pi) L <- with(K, sqrt(./pi)) plot(L) # compute 4 estimates of V(r) = L(r)/r V <- with(L, ./.x) plot(V) # compute the maximum absolute difference between # the isotropic and translation correction estimates of K(r) D <- with(K, max(abs(iso - trans)))
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