# creategroups: Creating Homogeneous Groups In biotools: Tools for Biometry and Applied Statistics in Agricultural Science

## Description

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.

## Usage

 `1` ```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 = ∑_{j}^{ngroups} abs( t_{j+1} - t_j ) / ngroups, where t_j = fun(group_j). If h ≤q 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(s)

Anderson Rodrigo da Silva <[email protected]>

## Examples

 ```1 2 3 4 5 6``` ```x <- rnorm(10, 1, 0.5) names(x) <- letters[1:10] creategroups(x, ngroups = 2, sizes = c(5, 5)) creategroups(x, ngroups = 3, sizes = c(3, 4, 3), tol = 0.05) # End (not run) ```

biotools documentation built on May 29, 2017, 7:48 p.m.