Compound Symmetry Correlation Structure

Usage

corCompSymm(value, form, fixed)

Arguments

value the correlation between any two correlated observations. Defaults to 0.
form a one sided formula of the form ~ t, or code{~ t | g}, specifying a time covariate t and, optionally, a grouping factor g. When a grouping factor is present in form, the correlation structure is assumed to apply only to observations within the same grouping level; observations with different grouping levels are assumed to be uncorrelated. Defaults to ~ 1, which corresponds to using the order of the observations in the data as a covariate, and no groups.
fixed an optional logical value indicating whether the coefficients should be allowed to vary in the optimization, or kept fixed at their initial value. Defaults to FALSE, in which case the coefficients are allowed to vary.

Description

This function is a constructor for the corCompSymm class, representing a compound symmetry structure corresponding to uniform correlation. Objects created using this constructor need to be later initialized using the appropriate initialize method.

Value

an object of class corCompSymm, representing a compound symmetry correlation structure.

Author(s)

Jose Pinheiro and Douglas Bates

References

Milliken, G. A. and Johnson, D. E. (1992) "Analysis of Messy Data, Volume I: Designed Experiments", Van Nostrand Reinhold.

See Also

initialize.corStruct

Examples

library(lme)
## covariate is observation order and grouping factor is Subject
cs1 <- corCompSymm(0.5, form = ~ 1 | Subject)

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