Re: st: Calculating average value using STATA program language

[Suryadipta Roy <sroy2138@gmail.com>]

Nick,
Thank you! I am sure that Stata has other ways (like using -foreach-
etc.) to arrive at the solution, and as Phil has suggested, probably
it was a good exercise in the long run for me to check out the
manuals. I am sure that I need to do lot more of that. I was actually
trying something like the follwing:

gen double avg=.
qui levelsof importer, local(clist)
foreach i of local clist {
su import if importer=="`i'", meanonly
qui replace avg=r(mean) if exporter=="`i'"
}


However, I understood that this is not going to work, since I did not
know a way to incorporate the industry categories (isic) in the
program. To sum it up, I clearly understand that I need to devote a
lot more time on the manuals, and the related materials to understand
Stata programming.

Sincerely,
Suryadipta.

On Mon, Sep 12, 2011 at 4:21 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> Suryadipta got excellent advice to look at -collapse- and the problem
> appears to be solved. However, if the main problem really had been
> misunderstanding of loops, it would have been hard to advise on the
> precise misunderstanding, as no Stata commands were included in this
> post. Saying exactly what you typed and what then happened is another
> key piece of advice.
>
> Nick
>
> On Mon, Sep 12, 2011 at 4:47 AM, Suryadipta Roy <sroy2138@gmail.com> wrote:
>
>> I am a newbie in terms of writing Stata codes, and intend to get that
>> corrected pretty soon. Meanwhile, I was wondering if any one could
>> help me with the following. I have been trying use foreach/forvalues
>> without any success for some time. Any help/suggestion/hint is greatly
>> appreciated.
>>
>> importer        exporter        year    isic     imports   sum_import   avg_import
>> AUS     FRA     1979    311     8       24      12
>> AUS     FRA     1980    311     16      24      12
>> AUS     FRA     1979    313     0       0       0
>> AUS     FRA     1980    313     0       0       0
>> AUS     GAB     1979    369     0       0       0
>> AUS     GBR     1976    311     10      30      10
>> AUS     GBR     1977    311     20      30      10
>> AUS     GBR     1978    311     0       30      10
>> AUT     CAN     1977    312     10      10      10
>> AUT     CAN     1978    390     20      20      20
>> FRA     AUS     1976    311     5       10      5
>> FRA     AUS     1977    311     5       10      5
>> FRA     AUT     1980    369     4        4      4
>>
>> In the hypothetical dataset above, I am trying to create the last two
>> columns (sum_import, and avg_import) from the "imports" column. For
>> the first column, the idea is to calculate the sum of imports e.g.
>> from FRA to AUS for each industry category (isic). Thus for the isic
>> category 311, the sum of imports in 1979 and 1980 is 8 + 16 = 24, and
>> the average in the two years is 12. Similarly, there were no trade
>> between AUS and GAB in 1979 for the industry category 369, and hence
>> the sum and the average value of imports = 0. The actual dataset has
>> over 200 countries covering data from 1976 - 1980 and I am trying to
>> calculate the average of the imports between 1976- 1980 in each
>> industry category. There are 28 such industry categories.
>>
>
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