Re: st: combination of k elements each being 0 or 1

[Fernando Rios Avila <f.rios.a@gmail.com>]

Hi Gregorio,
I do have a suggestion for the generalization of your algorithm. What
you are doing can be thought as the transformation from a number from
base 10 to base 2
It could go something like: (using your base code).
clear
local x 8
local n=2^`x'
set obs `n'
gen v0=""
forvalues i=1/`n' {
local n2=`i'-1
inbase 2 `n2'
return list
replace v0=r(base) in `i'
}

destring v0, replace

forvalues i=1/`x' {
gen v`i'=mod(v0,10)
replace v0=int(v0/10)
}

HTH
Fernando

On Tue, Mar 4, 2014 at 12:48 PM, Impavido, Gregorio <GImpavido@imf.org> wrote:
> Hello.
>
> I would like to define a matrix (2^k x k) with all possible combinations of k elements each being 0 or 1.  The code below produces what I want for k = 5 and can be modified for different values of k. My questions are:
>
> - Is there a matrix function in STATA or MATA that generalizes the code below for variable k?
> - If not, does anybody have suggestions on how to generalize the loop for variable k?
>
> Thank you in advance for your help
> Gregorio
>
>
>
> ******* begin example
> clear
> set more off
> local x 5
>
> local n = 2^`x'
> set obs `n'
>
> forvalues i = 1/`x' {
> gen v`i' = .
> }
>
> * set trace on
> local j = 1
> while `j' < `n' {
> forvalues i1 = 0/1 {
>         forvalues i2 = 0/1 {
>                 forvalues i3 = 0/1 {
>                         forvalues i4 = 0/1 {
>                                 forvalues i5 = 0/1 {
>                                         forvalues l = 1/`x' {
>                                                 replace v`l' = `i`l'' in `j'
>                                                 }
>                                                 local j = `j' + 1
>                                         }
>                                 }
>                         }
>                 }
>         }
> }
> ******* end example
>
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