Re: [Gretl-users] Function to get the powerset
On Mon, 22 Feb 2016, Henrique Andrade wrote:
Dear Gretl Community,
I really stuck trying to define a function that gives a power set of a
set. Suppose I have a set S:
S = {"A", "B", "C"}
The associated power set, P(S), is:
P(S) = {{ }, {"A"}, {"B"}, {"C"}, {"A",
"B"}, {"A", "C"}, {"B", "C"},
{"A", "B", "C"}}
All that I can think by now (shame on me!) is this:
strings S = defarray("A", "B", "C")
scalar P_S_len = 2^nelem(S) # the size of the power set
strings P_S = array(P_S_len) # an array with 8 spaces.
Does anyone have any ideas?
Maybe this is something you could build on:
<hansl>
strings S = defarray("A", "B", "C", "D")
scalar l = nelem(S)
matrix s = seq(0,2^l-1)'
matrix P = {}
scalar x = 2
loop l --quiet
a = s % 2
P ~= a
s = (s-a)/2
endloop
colnames(P,S)
print P
</hansl>
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Riccardo (Jack) Lucchetti
Dipartimento di Scienze Economiche e Sociali (DiSES)
Università Politecnica delle Marche
(formerly known as Università di Ancona)
r.lucchetti(a)univpm.it
http://www2.econ.univpm.it/servizi/hpp/lucchetti
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