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Re: st: -egen total()- function and indexing within the -if- condition


From   A Loumiotis <antonis.loumiotis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: -egen total()- function and indexing within the -if- condition
Date   Mon, 15 Apr 2013 14:24:13 +0300

Thanks a lot Maarten and Nick.  This clears up my misunderstanding.  I
should have read more carefully the helpfile of -egen-.

On Mon, Apr 15, 2013 at 2:19 PM, Nick Cox <njcoxstata@gmail.com> wrote:
> Whatever you see here is not a bug. The help for -egen- is explicit:
>
> "Explicit subscripting (using _N and _n), which is commonly used with
> -generate-, should not be used with -egen-"
>
> and that that applies to your syntax too. -egen- feels free to sort
> values temporarily and that makes any kind of subscripting unreliable.
>
> I'd assert that there is always a way round this, depending on what
> the real problem is.
>
> Nick
> njcoxstata@gmail.com
>
>
> On 15 April 2013 12:03, A Loumiotis <antonis.loumiotis@gmail.com> wrote:
>> Hi,
>>
>> I thought that the index number in the -if- condition is reseted to 1
>> at the beginning of every -by- group when generating a variable using
>> the -egen total()- function.  It seems that this is not the case
>> though as the example below demonstrates:
>>
>> ********
>> clear
>> input int i j x
>> 1 1 10
>> 1 2 0
>> 1 3 15
>> 2 1 15
>> 2 2 1
>> 2 3 20
>> end
>> bys i:gen s2x=sum(x) if x[2]==1 & inlist(j,1,3)
>> bys i:egen t2x=total(x) if x[2]==1 & inlist(j,1,3)
>> bys i:gen s5x=sum(x) if x[5]==1 & inlist(j,1,3)
>> bys i:egen t5x=total(x) if x[5]==1 & inlist(j,1,3)
>> li, sepby(i)
>>
>>      +------------------------------------+
>>      | i   j    x   s2x   t2x   s5x   t5x |
>>      |------------------------------------|
>>   1. | 1   1   10     .     .     .    25 |
>>   2. | 1   2    0     .     .     .     . |
>>   3. | 1   3   15     .     .     .    25 |
>>      |------------------------------------|
>>   4. | 2   1   15    15     .     .    35 |
>>   5. | 2   2    1     .     .     .     . |
>>   6. | 2   3   20    35     .     .    35 |
>>      +------------------------------------+
>>
>> *********
>>
>> I expected that t2x and t5x would be missing whenever s2x and s5x is
>> missing but it is not.  The results of the -sum()- function seems
>> logical to me given the -if- condition but not the results of the
>> -total()- function.  Is this the normal behavior of the -total()-
>> function or is this a bug?
>>
>> Best,
>> Antonis
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