freq.array               package:boot               R Documentation

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'

