freq.array: Bootstrap Frequency Arrays

In boot: Bootstrap Functions (Originally by Angelo Canty for S)

Bootstrap Frequency Arrays

Description

Take a matrix of indices for nonparametric bootstrap resamples and return the frequencies of the original observations in each resample.

Usage

freq.array(i.array)

Arguments

i.array

This will be an matrix of integers between 1 and n, where n is the number of observations in a data set. The matrix will have n columns and R rows where R is the number of bootstrap resamples. Such matrices are found by boot when doing nonparametric bootstraps. They can also be found after a bootstrap has been run through the function boot.array.

Value

A matrix of the same dimensions as the input matrix. Each row of the matrix corresponds to a single bootstrap resample. Each column of the matrix corresponds to one of the original observations and specifies its frequency in each bootstrap resample. Thus the first column tells us how often the first observation appeared in each bootstrap resample. Such frequency arrays are often useful for diagnostic purposes such as the jackknife-after-bootstrap plot. They are also necessary for the regression estimates of empirical influence values and for finding importance sampling weights.

See Also

boot.array

boot documentation built on Sept. 11, 2024, 6:15 p.m.