aliases {FrF2}R Documentation

Alias structure for fractional factorial 2-level designs

Description

Function to provide a human-friendly format for the alias structure of a fractional factorial 2-level design

Usage

aliases(fit, code = FALSE)

Arguments

fit a linear model object with only 2-level factors as x-variables; the function will return an error, if the model contains partially aliased effects (like interactions in a Plackett-Burman design for most cases)
code if TRUE, requests that aliasing is given in code letters (A, B, C etc.) instead of (potentially lengthy) variable names; in this case, a legend is included in the output object.

Value

A list with two elements:

legend links the codes to variable names, if code=TRUE.
aliases is a list of vectors of aliased effects.

Author(s)

Ulrike Groemping

References

Box G. E. P, Hunter, W. C. and Hunter, J. S. (2005) Statistics for Experimenters, 2nd edition. New York: Wiley.

See Also

FrF2-package for information on the package, alias for the built-in R-function, IAPlot for effects plots

Examples

    ### Injection Molding Experiment. Box et al. 1978.
    data(BM93.e3.data)  #from BsMD
    iMdat <- BM93.e3.data[1:16,2:10]  #only original experiment
    # make data more user-friendly
    colnames(iMdat) <- c("MoldTemp","Moisture","HoldPress","CavityThick",
             "BoostPress","CycleTime","GateSize","ScrewSpeed","y")
    # determine aliases with all 2-factor-interactions
    aliases(lm(y ~ (.)^2, data = iMdat))
    # coded version
    aliases(lm(y ~ (.)^2, data = iMdat), code=TRUE)
    # determine aliases with all 3-factor-interactions
    aliases(lm(y ~ (.)^3, data = iMdat), code=TRUE)
    # determine aliases for unaliased model
    aliases(lm(y ~ ., data = iMdat))

[Package FrF2 version 0.9-1 Index]