Creating Homogeneous Groups

A function to create homogeneous groups of named objects according to an objective function evaluated at a covariate. It can be useful to design experiments which contain a fixed covariate factor.

creategroups(x, ngroups, sizes, fun = mean, tol = 0.01, maxit = 200)

Arguments

x	a numeric vector of a covariate at which to evaluate the objective function.
ngroups	the number of groups to create.
sizes	a numeric vector of length equal to ngroups containing the group sizes.
fun	the objective function, i.e., to create groups with similar fun; default is mean.
tol	the tolerance level to define the groups as homogenenous; see details.
maxit	the maximum number of iterations; default is 200.

Details

creategroups uses a tol value to evaluate the following statistic: \(h = \sum_{j}^{ngroups} abs( t_{j+1} - t_j ) / ngroups\), where \(t_j = fun(group_j)\). If \(h \leq tol\), the groups are considered homogeneous.

Value

A list of

covar

a character indicating the name of the covariate.

func

a character indicating the name of the objective function.

val.func

a numeric vector containing the values evaluated by func on each group.

niter

the number of iteration require to achieve convergence.

labels

a list containing the labels of the objects in each group.

groups

a list of named vectors containing the values for the groups

Author

Anderson Rodrigo da Silva <anderson.agro@hotmail.com>

Examples

x <- rnorm(10, 1, 0.5)
names(x) <- letters[1:10]
creategroups(x, ngroups = 2, sizes = c(5, 5))
#> 
#> Creating homogeneous groups 
#> ------------------------------------------------------------------
#> Covariate: x 
#> 
#> Groups: 
#> $`1`
#> [1] "b" "c" "d" "e" "h"
#> 
#> $`2`
#> [1] "a" "f" "g" "i" "j"
#> 
#> Objective function (equality of): mean 
#>         1         2 
#> 0.9626447 0.9608447 
#> 
#> Number of iterations to convergence: 7 
creategroups(x, ngroups = 3, sizes = c(3, 4, 3), tol = 0.05)
#> 
#> Creating homogeneous groups 
#> ------------------------------------------------------------------
#> Covariate: x 
#> 
#> Groups: 
#> $`1`
#> [1] "a" "f" "g"
#> 
#> $`2`
#> [1] "d" "e" "h" "j"
#> 
#> $`3`
#> [1] "b" "c" "i"
#> 
#> Objective function (equality of): mean 
#>         1         2         3 
#> 1.0090613 0.9575708 0.9199934 
#> 
#> Number of iterations to convergence: 16 

# End (not run)