var.linear               package:boot               R Documentation

Linear Variance Estimate

Description:

     Estimates the variance of a statistic from its empirical influence
     values.

Usage:

     var.linear(L, strata=NULL)

Arguments:

       L: Vector of the empirical influence values of a statistic. 
          These will usually be calculated by a call to 'empinf'. 

  strata: A numeric vector or factor specifying which  observations
          (and hence empirical influence values) come from which
          strata. 

Value:

     The variance estimate calculated from 'L'.

References:

     Davison, A. C. and Hinkley, D. V. (1997) _Bootstrap Methods and
     Their Application_. Cambridge University Press.

See Also:

     'empinf', 'linear.approx', 'k3.linear'

Examples:

     #  To estimate the variance of the ratio of means for the city data.
     data(city)
     ratio <- function(d,w)
          sum(d$x * w)/sum(d$u * w)
     var.linear(empinf(data=city,statistic=ratio))

