aliases | R Documentation |
Functions to examine the alias structure of a fractional factorial 2-level design
aliases(fit, code = FALSE, condense=FALSE)
aliasprint(design, ...)
## S3 method for class 'aliases'
print(x, ...)
fit |
a linear model object with only 2-level factors as explanatory 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 |
x |
an object of class |
... |
further arguments to function |
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 |
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.
The output object of function aliases
has class aliases
,
which is used for customized printing with the print
method.
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, package="BsMD") #from BsMD
## iMdat <- BM93.e3.data[1:16,2:10] #only original experiment
## re-create here
y=c(14, 16.8, 15, 15.4, 27.6, 24, 27.4, 22.6,
22.3, 17.1, 21.5, 17.5, 15.9, 21.9, 16.7, 20.3)
iMdat <- FrF2(8,7,randomize=FALSE)
iMdat <- desnum(iMdat)
iMdat <- rbind(cbind(iMdat,H=1),cbind(-iMdat,H=-1))
iMdat <- cbind(as.data.frame(iMdat), y=y)
# 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))
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