# boot.array

##### Bootstrap Resampling Arrays

This function takes a bootstrap object calculated by one of the
functions `boot`

, `censboot`

, or `tilt.boot`

and
returns the frequency (or index) array for the bootstrap
resamples.

- Keywords
- nonparametric

##### Usage

`boot.array(boot.out, indices)`

##### Arguments

- boot.out
An object of class

`"boot"`

returned by one of the generation functions for such an object.- indices
A logical argument which specifies whether to return the frequency array or the raw index array. The default is

`indices=FALSE`

unless`boot.out`

was created by`tsboot`

in which case the default is`indices=TRUE`

.

##### Details

The process by which the original index array was generated is
repeated with the same value of `.Random.seed`

. If the frequency
array is required then `freq.array`

is called to convert the
index array to a frequency array.

A resampling array can only be returned when such a concept makes
sense. In particular it cannot be found for any parametric or
model-based resampling schemes. Hence for objects generated by
`censboot`

the only resampling scheme for which such an array can
be found is ordinary case resampling. Similarly if `boot.out$sim`

is `"parametric"`

in the case of `boot`

or `"model"`

in
the case of `tsboot`

the array cannot be found. Note also that
for post-blackened bootstraps from `tsboot`

the indices found
will relate to those prior to any post-blackening and so will not be
useful.

Frequency arrays are used in many post-bootstrap calculations such as the jackknife-after-bootstrap and finding importance sampling weights. They are also used to find empirical influence values through the regression method.

##### Value

A matrix with `boot.out$R`

rows and `n`

columns where
`n`

is the number of observations in `boot.out$data`

. If
`indices`

is `FALSE`

then this will give the frequency of
each of the original observations in each bootstrap resample. If
`indices`

is `TRUE`

it will give the indices of the
bootstrap resamples in the order in which they would have been passed
to the statistic.

##### Side Effects

This function temporarily resets `.Random.seed`

to the value in
`boot.out$seed`

and then returns it to its original value at the
end of the function.

##### See Also

##### Examples

```
# NOT RUN {
# A frequency array for a nonparametric bootstrap
city.boot <- boot(city, corr, R = 40, stype = "w")
boot.array(city.boot)
perm.cor <- function(d,i) cor(d$x,d$u[i])
city.perm <- boot(city, perm.cor, R = 40, sim = "permutation")
boot.array(city.perm, indices = TRUE)
# }
```

*Documentation reproduced from package boot, version 1.3-24, License: Unlimited*