Re: st: extraction and appending of data

[Nick Cox <njcoxstata@gmail.com>]

Unless the datasets are enormous, you can -keep- the observations for
-level==1- just once, in the final dataset. You don't (obviously) need
to loop around the datasets twice.

A presentation detail, but a troubling one for people who don't know
your data, is that you seemingly have a variable -level- and a local
macro -level- that aren't related. That is perfectly legal, but it
makes understanding your code just that bit harder.

Statalist can be tough: you get an opportunity to state your problem,
but if it's too difficult to understand, it will just get deleted.
Nobody is obliged to answer anything. Maximizing clarity is really
important.

Nick

On Tue, Apr 17, 2012 at 1:37 PM, Prakash Singh <prakashbhu@gmail.com> wrote:
> Dear stata listers
> I have following situation for which I am writing a stata programme
> code and I need all yours help in this. I have access to stata10.
>
> I am working with National Sample Survey Organiation data of India.
> The data for single round and particular subject comes in number of
> txt files. The structure of the txt file is such that it contains a
> particular group of variables for certain states in one txt file. thus
> to get information for all the states for that particular group of
> variable we need to append the extracted data. Here the group which
> identifies variable identifier is level i.e. level1 has particular
> list of variables.
>
> To put it in better way, suppose that whole data comes in 8 txt file
> and all the desired variables are divided into 10 levels, then we need
> to extract these 8 txt file for each level and append to get final
> data for individual level.
> The programme code which I have written in like this
>
> local level "11 12 13 14 15 16 17 18"
> foreach l of local level {
> infile using level`l'.dct
> keep if level==1
> save "level`l'.dta", replace
> }
> local levels "12 13 14 15 16 17 18"
> foreach l of local levels {
> use "level1.dta", clear
> append using "level`l'.dta"
> save "level1.dta", replace
> }
>
> Now the problem is that the code is only working for first txt file
> and after saving the level11.dta data whereas the outcome I was
> expecting is like level11.dta, ... level18.dta and then finally the
> appended level1.dta file.
>
> stata gives this error
> you must start with an empty dataset
> r(18);
>
>
>
> Thanks
> Prakash
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