StructurePickers | R Documentation |
Functions to restructure a fractional factorial by permuting the base factors such that the leftmost base factors have a suitable alias structure for the problem at hand; meant for expert users
splitpick(k, gen, k.WP, nfac.WP, show=10)
leftadjust(k, gen, early=NULL, show=10)
k |
the number of base factors (designs have |
gen |
vector of generating columns from Yates matrix |
k.WP |
integer number of base factors used for whole plot generation;
there will be |
nfac.WP |
integer number of whole plot factors, must not be smaller than |
show |
numeric integer indicating how many results are to be shown;
for function |
early |
number that indicates how many “leftmost” factors are
needed in the design; used by |
These functions exploit the fact that a factorial design can be arranged such
that the 2^k.WP-1
leftmost columns have exactly 2^k.WP
different patterns. They can thus accomodate whole plot effects if 2^k.WP
plots are available; also, with a specially rearranged version of the Yates matrix,
the leftmost columns can have particularly few or particularly many level changes,
cf. e.g. Cheng, Martin and Tang 1998.
By permuting the k
base factors , the functions try to find 2^k.WP
ones that accomodate the current needs, if taken as the first base factors. They are
used by function FrF2
, if a user requests an automatically-generated
split-plot design or a design with some factors declared hard-to-change.
There may be a possibility to better accomodate the experimenters needs within
a given design by trying different sets of base factors. This is not done
in these functions. Also, custom user needs may be better fulfilled, if an expert
user directly uses one of these functions for inspecting the possibilities, rather
than relying on the automatic selection routine in function FrF2
.
Both functions output a list of entries with information on at most show
suitable
permutations. splitpick
ends with an error, if no suitable
solution can be found.
orig |
original generator column numbers |
basics |
named vector with the following entries: |
perms |
matrix with rows containing permutations of base factors |
res.WP |
for |
maxpos |
for |
k.early |
for |
gen |
matrix the rows of which contain the generator columns for the respective rows of perms |
Ulrike Groemping
Cheng, C.-S., Martin, R.J., and Tang, B. (1998). Two-level factorial designs with extreme numbers of level changes. Annals of Statistics 26, 1522-1539.
See Also FrF2
## leftadjusting MA design from table 6.22 in BHH2, 9 factors, 32 runs
## NOTE: nevertheless not as well left-adjusted as the isomorphic design 9-4.1 from catlg
leftadjust(5,c(30,29,27,23))
## with option early=4 (i.e. 4 columns as early as possible are requested)
leftadjust(5,c(30,29,27,23),early=4)
leftadjust(5,catlg$'9-4.1'$gen,early=4)
## look for a split plot design in 32 runs with 7 factors,
## 3 of which are whole plot factors,
## and 8 plots
splitpick(5,catlg$'7-2.1'$gen,nfac.WP=3,k.WP=3)
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