These functions identify the positions for cube points or star points and can reduce a central composite design to its cube portion (with center points).
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a data frame of class design that contains a 2-level fractional factorial (regular or non-regular) or a central composite design.
currently not used
iscube provides a logical vector that is TRUE for cube points
and FALSE for center points and star points. Its purpose is to enable use of simple functions
for “clean” 2-level fractional factorials like
isstar provides a logical vector that is TRUE for the star block
(including center points) of a central composite design.
pickcube reduces a central composite design (type
to its cube block, including center points. This function is needed, if a CCD
has been created in one go, but analyses are already required after conducting
the cube portion of the design (and these perhaps even prevent the star portion
from being run at all).
isstar each return a logical vector (cf. Details section).
pickcube returns a data frame of class design with
For version 0.22-8 of package DoE.base, function
iscube returned a wrong result
without warning, when applied to an old version CCD design
(before DoE.wrapper, version 0.8-6 of Nov 15 2011).
Since version 0.23 of package DoE.base, the function works on old designs, except for blocked or replicated versions; for these, an error is thrown.)
The functions have not been tested for central composite designs for which the cube portion itself is blocked.
Montgomery, D.C. (2001). Design and Analysis of Experiments (5th ed.). Wiley, New York.
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