Create a Function Value Table
Advanced Use Only.
This low-level function creates an object of class "fv"
from raw numerical data.
fv(x, argu = "r", ylab = NULL, valu, fmla = NULL, alim = NULL, labl = names(x), desc = NULL, unitname = NULL, fname = NULL, yexp = ylab)
x |
A data frame with at least 2 columns containing the values of the function argument and the corresponding values of (one or more versions of) the function. |
argu |
String. The name of the column of |
ylab |
Either |
valu |
String. The name of the column of |
fmla |
Either |
alim |
Optional. The default range of values of the function argument for which the function will be plotted. Numeric vector of length 2. |
labl |
Optional. Plot labels for the columns of |
desc |
Optional. Descriptions of the columns of |
unitname |
Optional. Name of the unit (usually a unit of length) in which the function argument is expressed. Either a single character string, or a vector of two character strings giving the singular and plural forms, respectively. |
fname |
Optional. The name of the function itself. A character string. |
yexp |
Optional. Alternative form of |
This documentation is provided
for experienced programmers who want to modify the internal
behaviour of spatstat. Other users please see fv.object.
The low-level function fv is used to create an object of
class "fv" from raw numerical data.
The data frame x contains the numerical data.
It should have one column
(typically but not necessarily named "r")
giving the values of the function argument for which
the function has been evaluated; and at least one other column,
containing the corresponding values of the function.
Typically there is more than one column of function values. These columns typically give the values of different versions or estimates of the same function, for example, different estimates of the K function obtained using different edge corrections. However they may also contain the values of related functions such as the derivative or hazard rate.
argu specifies the name of the column of
x that contains the values of the function argument
(typically argu="r" but this is not compulsory).
valu specifies the name of another column
that contains the ‘recommended’ estimate of the function.
It will be used to provide function values in those situations where
a single column of data is required. For example,
envelope computes its simulation envelopes
using the recommended value of the summary function.
fmla specifies the default plotting behaviour.
It should be a formula, or a string that can be converted to a
formula. Variables in the formula are names of columns of x.
See plot.fv for the interpretation of this
formula.
alim specifies the recommended range of the
function argument. This is used in situations where statistical
theory or statistical practice indicates that the computed
estimates of the function are not trustworthy outside a certain
range of values of the function argument. By default,
plot.fv will restrict the plot to this range.
fname is a string giving the name of the function itself.
For example, the K function would have fname="K".
ylab is a mathematical expression
for the function value, used when labelling an axis
of the plot, or when printing a description of the
function. It should be an R language object.
For example the K function's mathematical name K(r) is rendered
by ylab=quote(K(r)).
If yexp is present, then ylab will be
used only for printing, and yexp will be used for
annotating axes in a plot. (Otherwise yexp defaults to ylab).
For example the cross-type K function
K[1,2](r) is rendered by something like
ylab=quote(Kcross[1,2](r))
and
yexp=quote(Kcross[list(1,2)](r))
to get the most satisfactory behaviour.
(A useful tip: use substitute instead of
quote to insert values of variables into an expression,
e.g. substitute(Kcross[i,j](r), list(i=42,j=97))
yields the same as quote(Kcross[42, 97](r)).)
labl is a character vector specifying plot labels
for each column of x. These labels will appear on the
plot axes (in non-default plots), legends and printed output.
Entries in labl
may contain the string "%s" which will be replaced
by fname. For example the border-corrected estimate
of the K function has label "%s[bord](r)" which
becomes "K[bord](r)".
desc is a character vector containing intelligible
explanations of each column of x. Entries in
desc may contain the string "%s" which will be replaced
by ylab. For example the border correction estimate of the
K function has description "border correction estimate of %s".
An object of class "fv", see fv.object.
Adrian Baddeley Adrian.Baddeley@curtin.edu.au
and Rolf Turner r.turner@auckland.ac.nz
See plot.fv for plotting an "fv" object.
See as.function.fv to convert an "fv" object
to an R function.
The functions fvnames, fvnames<- allow the user to
use standard abbreviations to refer to columns of an "fv" object.
Undocumented functions for modifying an "fv" object
include tweak.fv.entry and rebadge.fv.
df <- data.frame(r=seq(0,5,by=0.1))
df <- transform(df, a=pi*r^2, b=3*r^2)
X <- fv(df, "r", quote(A(r)),
"a", cbind(a, b) ~ r,
alim=c(0,4),
labl=c("r", "%s[true](r)", "%s[approx](r)"),
desc=c("radius of circle",
"true area %s",
"rough area %s"),
fname="A")
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