fv
Create a Function Value Table
Advanced Use Only.
This low-level function creates an object of class "fv"
from raw numerical data.
Usage
fv(x, argu = "r", ylab = NULL, valu, fmla = NULL, alim = NULL, labl =
names(x), desc = NULL, unitname = NULL, fname = NULL, yexp = ylab)
Arguments
- 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
x
that contains the values of the function argument. - ylab
- Either
NULL
, or an Rlanguage expression representing the mathematical name of the function. See Details. - valu
- String. The name of the column of
x
that should be taken as containing the function values, in cases where a single column is required. - fmla
- Either
NULL
, or aformula
specifying the default plotting behaviour. See Details. - 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
x
. A vector of strings, with one entry for each column ofx
. - desc
- Optional. Descriptions of the columns of
x
. A vector of strings, with one entry for each column ofx
. - 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
ylab
more suitable for annotating an axis of the plot. See Details.
Details
This documentation is provided
for experienced programmers who want to modify the internal
behaviour of 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 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 Rlanguage object.
For example the $K$ function's mathematical name $K(r)$ is rendered
by ylab=substitute(K(r), NULL)
.
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=substitute(Kcross[i,j](r), list(i=1,j=2))
and
yexp=substitute(Kcross[list(i,j)](r), list(i=1,j=2))
to get the most satisfactory behaviour.
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 "%sbord(r)"
which
becomes "Kbord(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"
.
Value
- An object of class
"fv"
, seefv.object
.
See Also
See plot.fv
for plotting an "fv"
object.
See as.function.fv
to convert an "fv"
object
to an Rfunction.
Use cbind.fv
to combine several "fv"
objects.
Use bind.fv
to glue additional columns onto an existing
"fv"
object.
Undocumented functions for modifying an "fv"
object
include fvnames
, fvnames<-
,
tweak.fv.entry
and rebadge.fv
.
Examples
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", substitute(A(r), NULL),
"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")
X