pairs.boot: Two sample bootstrap.
In simpleboot: Simple Bootstrap Routines

Description Usage Arguments Value Author(s) Examples

pairs.boot is used to bootstrap a statistic which operates on two samples and returns a single value. An example of such a statistic is the correlation coefficient (i.e. cor). Resampling is done pairwise, so x and y must have the same length (and be ordered correctly). One can alternatively pass a two-column matrix to x.

1	pairs_boot(x, y = NULL, FUN, R, student = FALSE, M, weights = NULL, ...)

`x`	Either a vector of numbers representing the first sample or a two column matrix containing both samples.
`y`	If NULL it is assumed that `x` is a two-column matrix. Otherwise, `y` is the second sample.
`FUN`	The statistic to bootstrap. If `x` and `y` are separate vectors then `FUN` should operate on separate vectors. Similarly, if `x` is a matrix, then `FUN` should operate on two-column matrices. `FUN` can be either a quoted string or a function name.
`R`	The number of bootstrap replicates.
`student`	Should we do a studentized bootstrap? This requires a double bootstrap so it might take longer.
`M`	If `student` is set to `TRUE`, then `M` is the number of internal bootstrap replications to do.
`weights`	Resampling weights.
`...`	Other (named) arguments that should be passed to `FUN`.

An object of class "simpleboot", which is almost identical to the regular "boot" object. For example, the boot.ci function can be used on this object.

Roger D. Peng

library(boot)
set.seed(1)
x <- rnorm(100)
y <- 2 * x + rnorm(100)
boot.cor <- pairs_boot(x, y, FUN = cor, R = 100)
boot.ci(boot.cor)

Simple Bootstrap Routines (1.1-7)
BOOTSTRAP CONFIDENCE INTERVAL CALCULATIONS
Based on 100 bootstrap replicates

CALL : 
boot.ci(boot.out = boot.cor)

Intervals : 
Level      Normal              Basic         
95%   ( 0.8409,  0.9318 )   ( 0.8394,  0.9442 )  

Level     Percentile            BCa          
95%   ( 0.8204,  0.9251 )   ( 0.8217,  0.9265 )  
Calculations and Intervals on Original Scale
Some basic intervals may be unstable
Some percentile intervals may be unstable
Some BCa intervals may be unstable
Warning message:
In boot.ci(boot.cor) : bootstrap variances needed for studentized intervals