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RE: st: RE: limitations of "generate" with missing data


From   "Fernando Rios Avila" <[email protected]>
To   <[email protected]>
Subject   RE: st: RE: limitations of "generate" with missing data
Date   Mon, 11 Apr 2011 18:19:17 -0400

Apologies, it was a typo
>  set obs 1000
> gen r=runiform()
>  replace  r=. if runiform()>.5
>  gen r2=r>0.7 if r!=.


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Nick Cox
Sent: Monday, April 11, 2011 6:18 PM
To: [email protected]
Subject: Re: st: RE: limitations of "generate" with missing data

What is r1?

On Mon, Apr 11, 2011 at 11:09 PM, Fernando Rios Avila <[email protected]>
wrote:
> Hi Michael,
> The limitation is not with generate. But rather with the way u are 
> creating your dummy variable I think this should do the trick
>
>  set obs 1000
> gen r=runiform()
>  replace  r=. if runiform()>.5
>  gen r2=r>0.7 if r1!=.
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Michael 
> Costello
> Sent: Monday, April 11, 2011 6:01 PM
> To: statalist
> Subject: st: limitations of "generate" with missing data
>
> Statalisters,
>
> I recently ran into a problem with the following dataset:
>
> . tab  gread_comp_score_pcnt, m
> gread_comp_ |
>  score_pcnt |      Freq.     Percent        Cum.
> ------------+-----------------------------------
>          0 |        150        7.50        7.50
>         .2 |         85        4.25       11.75
>         .4 |         97        4.85       16.60
>         .6 |         82        4.10       20.70
>         .8 |         72        3.60       24.30
>          1 |         15        0.75       25.05
>          . |      1,499       74.95      100.00
> ------------+-----------------------------------
>      Total |      2,000      100.00
>
> The high number of "missing" is by design, a by-product of a 
> horizontally structured dataset that I have yet to rectify.
>
> When I run the command:
> gen gread_comp_score_pcnt80= (gread_comp_score_pcnt>.79) I am left 
> with
>
> . tab  gread_comp_score_pcnt80, m
> gread_comp_ |
> score_pcnt8 |
>          0 |      Freq.     Percent        Cum.
> ------------+-----------------------------------
>          0 |        414       20.70       20.70
>          1 |      1,586       79.30      100.00
> ------------+-----------------------------------
>      Total |      2,000      100.00
>
> As you can see, the 87 values above .79 were set to 1, but so were all 
> the missing values!!  I have toyed with the code a bit, trying 
> variations such as . gen gread_comp_score_pcnt80= 
> (gread_comp_score_pcnt>.79 &
> gread_comp_score_pcnt!=.)
> but that converts all the missing to 0's, which is only marginally better.
>
> So the question is, is there some way to use a single, precise line of 
> code to create eighty-seven 1's, four hundred fourteen  0's and 1499 
> Missing values in one dummy variable?  I know I can do it with several 
> lines of code, but I'm looking for something more concise, as it needs 
> to run many hundreds of times.
>

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