Modify support of pdqr-function using method of choice.
form_resupport(f, support, method = "reflect")
Numeric vector with two increasing (or non-decreasing, see
Details) elements describing support of the output. Values can be
Resupport method. One of "reflect", "trim", "winsor", "linear".
Method "reflect" takes a density "tails" to the left of
and to the right of
support and reflects them inside
support. It means
that values of density inside and outside of supplied
support are added
together in "symmetric fashion":
d(x) = d_f(x) + d_f(l - (x-l)) + d_f(r + (r-x)), where
d_f is density of
d is density of output,
r are left and right edges of
support. This option is useful for repairing support of
new_*()'s output, as by default kernel density estimation in
density() adds tails to the range of input
x values. For example, if
there is a need to ensure that distribution has only positive values, one can
form_resupport(f, c(0, NA), method = "reflect"). Notes:
For "discrete" pdqr-functions that might result into creating new "x" values of distribution.
support is done only if it is strictly greater than
f's left edge of support. Reflection over
support - if
edge is strictly smaller.
Method "trim" removes density "tails" outside of
support, normalizes the
rest and creates appropriate pdqr-function.
Method "winsor" makes all density "tails" outside of input
"squashed" inside it in "dirac-like" fashion. It means that probability from
both tails is moved inside
support and becomes concentrated in
neighborhood of nearest edge. This models a singular dirac distributions at
the edges of
support. Note that
support can represent single point,
in which case output has single element if
f's type is "discrete" or is a
dirac-like distribution in case of "continuous" type.
Method "linear" transforms
f's support linearly to be input
f's support is [0; 1] and
c(-1, 1), linear
resupport is equivalent to
2*f - 1. Note that
support can represent
single point with the same effect as in "winsor" method.
form_regrid() for changing grid (rows of "x_tbl" metadata) of
form_retype() for changing type of pdqr-function.
set.seed(101) d_norm <- as_d(dnorm) d_dis <- new_d(data.frame(x = 1:4, prob = 1:4/10), "discrete") # Method "reflect" plot(d_norm)# For "discrete" functions it might create new values meta_x_tbl(form_resupport(d_dis, c(NA, 2.25), "reflect"))#> x prob cumprob #> 1 1.0 0.1666667 0.1666667 #> 2 1.5 0.5000000 0.6666667 #> 3 2.0 0.3333333 1.0000000# This is often useful to ensure constraints after `new_()` x <- runif(1e4) d_x <- new_d(x, "continuous") plot(d_x)# Method "trim" plot(d_norm)# Method "winsor" plot(d_norm)# Method "linear" plot(d_norm)