Re: AW: st: random draw of single variable, not whole data

[Jeph Herrin <junk@spandrel.net>]

You're right about the missings; I didn't get any but
I could have. Maybe

   gen y = x[ceil(_N*uniform())]

as long as uniform() never returns precisely 0, which I've
never seen - can it?

But certainly there's no reference to the values that x takes;
a random observation number is generated in (1,...,_N) and y is
set equal to that observation on x. So yes, it handles whatever
x looks like, I'm merely sampling from the list of observation
numbers.

J




Martin Weiss wrote:
> <> 
>
>
> Your "with replacement" method leads to missings every now and then. Apart
> from that, if Florian had an irregularly spaced list of numbers to sample
> from, which also need not be integers, would your method be capable of
> handling that?
>
>
>
> HTH
> Martin
>
>
> -----Ursprüngliche Nachricht-----
> Von: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Jeph Herrin
> Gesendet: Donnerstag, 26. Februar 2009 20:20
> An: statalist@hsphsun2.harvard.edu
> Betreff: Re: st: random draw of single variable, not whole data
>
>
> It's not clear if you want sampling with or without replacement.
>
> With replacement:
>
>    gen y = x[round(_N*uniform(),1)+1]
>
> without replacement:
>
>    egen index=rank(uniform())
>    gen y = x[index]
>
> hth,
> Jeph
>
>
> Florian Wakolbinger wrote:
> > Dear all,
> >
> > is it possible to randomly draw numbers out of a variable x and write it 
> > into another variable y
> >
> > i.e. if
> >
> > x
> > 1
> > 2
> > 3
> > 4
> > 5
> >
> > then y could be, for instance
> >
> > y
> > 3
> > 5
> > 3
> > 2
> > 4
> >
> > all numbers in y are randomly drawn from x. how is it possible to 
> > construct such a variable y in stata?
> >
> > thanks, and kind regards
> > florian
> >
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