| aliases {FrF2} | R Documentation |
Functions to examine the alias structure of a fractional factorial 2-level design
aliases(fit, code = FALSE, condense=FALSE) aliasprint(design, ...)
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. |
condense |
if TRUE, reformats the alias information to be comparable to the version calculated by internal function alias3fi; does not work with models with higher than 3-way interactions; for up to 3-way interactions, the output may be more easily readible |
design |
a data frame of class design that should contain a fractional factorial 2-level design; the function does not print anything if the design is of different nature |
... |
further arguments to function print.default |
Function aliasprint returns NULL and is called for its side effects only.
Per default, Function aliases returns a list with two elements:
legend |
links the codes to variable names, if code=TRUE. |
aliases |
is a list of vectors of aliased effects. |
If option condense is TRUE, the function returns a list with elements legend,
main, fi2 and fi3; this may be preferrable for looking at the alias structure of larger designs.
Ulrike Groemping
Box G. E. P, Hunter, W. C. and Hunter, J. S. (2005) Statistics for Experimenters, 2nd edition. New York: Wiley.
FrF2-package for information on the package,
alias for the built-in R-function,
IAPlot for effects plots
### 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)
# show condensed form
aliases(lm(y ~ (.)^3, data = iMdat), code=TRUE, condense=TRUE)
# determine aliases for unaliased model
aliases(lm(y ~ ., data = iMdat))