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Re: st: Evaluate if a dataset is empty
From
Nick Cox <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: Evaluate if a dataset is empty
Date
Thu, 27 Mar 2014 11:09:19 +0000
Given other answers, I want to stress that you don't need to read in a
dataset to establish that's it's empty. That said, reading in an empty
dataset is pretty fast.
Nick
[email protected]
On 27 March 2014 11:07, Nick Cox <[email protected]> wrote:
> There are two parts. The first part is that you can find out remotely
> that a dataset is empty by
>
> describe using foo
>
> and establishing whether r(N) == 0.
>
> The second is that you are planning to create about 10,000 datasets
> with not much in them. I would instead create a list of names of empty
> datasets in a local macro, and then with that create a composite
> dataset with the same stuff, all just once.
>
> An overarching question is why you need to pretend that empty datasets
> are populated, but I guess there is a good reason.
> Nick
> [email protected]
>
>
> On 27 March 2014 10:51, Seliger Florian <[email protected]> wrote:
>> Dear Statalist
>>
>> I want Stata to go through 20,000 small datasets (with a forvalues loop, datasets are indexed accordingly) and evaluate if the dataset is empty or not. About 50% of the datasets are empty meaning that there are no values for any variable.
>> Please note that the variables are the same across all datasets.
>>
>> For empty datasets, Stata is asked to create observations, to generate an identifier and to set all values equal to zero (except for the identifier):
>>
>> set obs 18
>> bys id: replace id=_n
>>
>> forvalues k=1(1)18 {
>> replace ind `k'=0 if ind`k'==.
>> }
>>
>>
>> At the end, I want to merge datasets based on "id". It is important that empty datasets are included and contain zeros.
>>
>>
>> My problem is that I do not know how to ask STATA to evaluate whether a dataset is empty or not.
>> Before "set obs 18" STATA does not recognize that values are missing meaning that there is simply "nothing" in the dataset.
>> How can I ask STATA to identify that there is "nothing" within my loop (forvalues i=1(1).)?
>>
>> Thanks a lot,
>> Florian
>>
>>
>>
>> *
>> * For searches and help try:
>> * http://www.stata.com/help.cgi?search
>> * http://www.stata.com/support/faqs/resources/statalist-faq/
>> * http://www.ats.ucla.edu/stat/stata/
*
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