Hello,
Martin and Nick, thank you so much. Your suggestion works very well.
I am sorry for being unclear about my question.
I will clarify it now. I have a large dataset around 1 million records. There are
around 20 variables. I would like to run the clogit regression, which requires me
to reshape the data into the long form. Basically, it is the model of a person
choosing a product from the choice set of 12. Thus, the total records would be of
12 million after reshaping.
In the beginning, I tried with the smaller sample and reshape worked very slow.
Then, I thought I should start with only 2 ID variables: person ID and choice ID (1-12).
I created the wide form data of only 2 ID variables, reshaped it to the long form, and
lastly merged other variables that are associate with person and choice respectively.
However, even with the only 2 ID variables, it took a long time for reshape to finish
for the small sample of the total 1 million records. That is why I try to find the
faster way to create the empty dataset with 2 ID variables first. Then my next step
is to merge the information about a person and the choice.
I hope this is clear enough. And if you and others have other better approach to
prepare the data like this, please let me know. There are a lot more for me to learn
from all of you.
Thank you,
Anupit
----- "Nick Cox" <[email protected]> wrote:
> Martin's advice looks good.
>
> But Anupit's question doesn't hang together for me. The specific
> example, and even longer ones of the same form, don't strike me as
> -reshape- questions at all as they involve creating new data in
> structured form.
>
> By the way, for large datasets make sure to use -egen long- or -egen
> double- if you need to.
>
> But if you had a -reshape- question, strict sense, I doubt you could
> speed things up much by programming it yourself with -forvalues- or
> -foreach-. That would, broadly speaking, mean that you were a better
> Stata programmer than the Stata developers. There could well be
> exceptions, but I'd guess that this statement would be true much more
> often than its converse.
>
> Nick
> [email protected]
>
> Martin Weiss
>
> - h egen,seq()-
>
> Supnithadnaporn, Anupit
>
> Would you please suggest me how to create data in the long form
> by *not* using reshape? I would like to avoid reshape because reshape
> takes very very long time. In fact, the final & total number of
> records
> that I have to create would be around 12,000,000.
>
> I think foreach and forvalues can do this work.
> But, I am a novice in Stata programming and could not figure out so
> far.
>
> In the beginning, I have only Obsid which is created by
>
> gen Obsid = _n
>
> The desired data would look like this:
>
> Obsid Vid Imp
> 1 1 1
> 2 1 2
> 3 1 3
> 4 1 4
> 5 2 1
> 6 2 2
> 7 2 3
> 8 2 4
>
> ...
>
>
> 100 25 4
>
>
> *
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