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
```