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st: Re: problem with -capture drop-


From   "Steichen" <[email protected]>
To   <[email protected]>
Subject   st: Re: problem with -capture drop-
Date   Tue, 21 Oct 2003 16:55:01 -0400

Eddy writes:

> I encountered an odd behavior of -capture drop-, and would appreciate
> advice.
> 
> I have a program in which a variable called "resid" was created
> first, and another variable "r" was created later. Before creating
> "r", I want to make sure that there is no existing variable sharing
> the same name. So I issue
> 
>      capture drop r
> 
> to make sure there is no "r" before it is created. The problem is,
> the above line also drops "resid" which I'd like to keep it there.
> The symptom can be illustrated as the follows.
> 
> ---------- example -------------------
> . set obs 100
> obs was 0, now 100
> 
> . gen resid = 1
> 
> .
> . sum resid
> 
>     Variable |       Obs        Mean    Std. Dev.       Min       
> Max
> -------------+--------------------------------------------------------
>        resid |       100           1           0          1         
> 1
> 
> .
> . capture drop r
> 
> .
> . sum resid
> no variables defined
> r(111);
> 
> -------- end of example -------
> 
> This is true for both Stata 7, 7SE, and 8SE. My question: Is this the
> intended behavior? Is there anyway to tell Stata to drop only those
> literally specified? Thanks.


Eddy -

I'm running fully updated Stata/SE 8.1 and do not get the same result:

. l

     +----------------------+
     | r1   rrr   resid   r |
     |----------------------|
  1. |  3     3       4   2 |
  2. |  3     3       4   2 |
  3. |  3     3       4   2 |
  4. |  3     3       4   2 |
  5. |  3     3       4   2 |
     |----------------------|
  6. |  3     3       4   2 |
  7. |  3     3       4   2 |
  8. |  3     3       4   2 |
  9. |  3     3       4   2 |
 10. |  3     3       4   2 |
     +----------------------+

. capture drop r

. l

     +------------------+
     | r1   rrr   resid |
     |------------------|
  1. |  3     3       4 |
  2. |  3     3       4 |
  3. |  3     3       4 |
  4. |  3     3       4 |
  5. |  3     3       4 |
     |------------------|
  6. |  3     3       4 |
  7. |  3     3       4 |
  8. |  3     3       4 |
  9. |  3     3       4 |
 10. |  3     3       4 |
      +------------------+

As you can see, only variable r was dropped.

Perhaps you should restart Stata or be sure you have the lastest version.

Tom


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