[R] An index of all possible combinations of variables in a data fram e
Gabor Grothendieck
ggrothendieck at myway.com
Tue Sep 28 07:13:11 CEST 2004
Alan Simpson <alan.simpson <at> robertsresearch.com.au> writes:
: Does anybody know of any way to create an index of all the possible
: combinations of variables (factors) in a data frame? ie for 3 factors A, B &
: C we have
:
: A
: B
: C
: AB
: AC
: BC
: ABC
:
: which equates to columns 1, 2, 3, 1:2, (1,3), 2:3 and 1:3.
:
: I realise that a function like model.matrix does this, but how to get the
: seqence of the index?
:
Is this what you are looking for?
R> attributes(terms(~ a * b * c))$term.labels
[1] "a" "b" "c" "a:b" "a:c" "b:c" "a:b:c"
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