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

 From "Martin Weiss" To Subject AW: AW: st: random draw of single variable, not whole data Date Thu, 26 Feb 2009 20:46:35 +0100

```<>

-set seed- to get one @ obs no 4

*************
clear
input x
1
2
3
4
5
6
7
8
9
10
end
set seed 100173
gen y = x[round(_N*uniform(),1)+1]
l
*************

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 20:41
An: statalist@hsphsun2.harvard.edu
Betreff: Re: AW: st: random draw of single variable, not whole data

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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>>
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>
>
> *
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> *   http://www.ats.ucla.edu/stat/stata/
>

*
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*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```

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