Modify support of pdqr-function using method of choice.
form_resupport(f, support, method = "reflect")
f | A pdqr-function. |
---|---|
support | Numeric vector with two increasing (or non-decreasing, see
Details) elements describing support of the output. Values can be |
method | Resupport method. One of "reflect", "trim", "winsor", "linear". |
A pdqr-function with modified support and the same
class and type as f
.
Method "reflect" takes a density "tails" to the left of support[1]
and to the right of support[2]
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
input, d
is density of output, l
and r
are left and right edges of
input 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
do form_resupport(f, c(0, NA), method = "reflect")
. Notes:
For "discrete" pdqr-functions that might result into creating new "x" values of distribution.
Reflection over support[1]
is done only if it is strictly greater than
f
's left edge of support. Reflection over support[2]
- if f
's right
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 support
"squashed" inside it in "dirac-like" fashion. It means that probability from
both tails is moved inside support
and becomes concentrated in 1e-8
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 support
. For
example, if f
's support is [0; 1] and support
is 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
pdqr-function.
form_retype()
for changing type of pdqr-function.
Other form functions:
form_estimate()
,
form_mix()
,
form_regrid()
,
form_retype()
,
form_smooth()
,
form_tails()
,
form_trans()
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