nelder {glmmrBase}

Generates a block experimental structure using Nelder's formula

Description

Generates a data frame expressing a block experimental structure using Nelder's formula

Usage

nelder(formula)

Arguments

formula

A model formula. See details

Details

Nelder (1965) suggested a simple notation that could express a large variety of different blocked designs. The function 'nelder()' that generates a data frame of a design using the notation. There are two operations:

'>' (or \to in Nelder's notation) indicates "clustered in".

'*' (or \times in Nelder's notation) indicates a crossing that generates all combinations of two factors.

The implementation of this notation includes a string indicating the name of the variable and a number for the number of levels, such as 'abc(12)'. So for example '~cl(4) > ind(5)' means in each of five levels of 'cl' there are five levels of 'ind', and the individuals are different between clusters. The formula '~cl(4) * t(3)' indicates that each of the four levels of 'cl' are observed for each of the three levels of 't'. Brackets are used to indicate the order of evaluation. Some specific examples:

'~person(5) * time(10)': A cohort study with five people, all observed in each of ten periods 'time'

'~(cl(4) * t(3)) > ind(5)': A repeated-measures cluster study with four clusters (labelled 'cl'), each observed in each time period 't' with cross-sectional sampling and five indviduals (labelled 'ind') in each cluster-period.

'~(cl(4) > ind(5)) * t(3)': A repeated-measures cluster cohort study with four clusters (labelled 'cl') wth five individuals per cluster, and each cluster-individual combination is observed in each time period 't'.

'~((x(100) * y(100)) > hh(4)) * t(2)': A spatio-temporal grid of 100x100 and two time points, with 4 households per spatial grid cell.

Value

A list with the first member being the data frame

Examples

nelder(~(j(4) * t(5)) > i(5))
nelder(~person(5) * time(10))