Re: [Gretl-users] Manipulating a database

On Sat, 3 Apr 2010, Leandro Zipitria wrote: Hello Gretl Community, > > I have a database with daily prices which is in a rather unusual format > and I want to know if it is possibly to create a panel data with it using > Gretl scripts. The database is > extracted from a dbf archive, and its has 6 variables: > > - The (number of) supermarket from which the price is reported > - The (number of) the product which price is being reported > - The year of the price > - The month of the price > - The price reported itself > - The first day of the month the price is reported > - The last day of the month the price is reported > > I have nearly one million rows with data, but in order to do some > regressions -and use it as a panel- I will need to transform it in a > suitable way. > > I suppose that the best way that Gretl can handle it is to create a > specific column for each product, and then stack all the supermarkets on a > daily basis. In this way, I will > have each column representing a product, the first 700 rows being a price > for each product for supermarket 1, the next 700 rows being a price for each > product for supermarket > 2, etc. > But in order to do it, I will need first to create the daily prices > series, which is now "compacted" in the datafile. I am attaching a random 10 > elements from the database in > order to get a better picture of the situation. In the first sheet I > submit the actual data format, on the second one which I think should be the > (best?) result. > > I will first ask if this kind of transformation is possible in Gretl. I am > aware that running some scripts on other programs could do the trick, but I > think that it could be > possible in Gretl to do it. But I am also think that it could be rather > complex to do it, and I am a new one on this issues. > Two remarks/suggestions: 1) Turning a dataset such as this into a panel dataset is not trivial from a _conceptual_ point of view: what are your units? supermarkets or products? or combinations of the two? What would you use as the time unit (day, month, week)? If you choose anything longer than a day (say, a week), how would you handle changes of prices during the week? Of course, this is a design decision and gretl can't help you with this. 2) If you have your data in some database that can be queried via SQL, I think that our ODBC apparatus may just fit your needs. You may want to have a look at the corresponding chapter of the User's Guide. Riccardo (Jack) Lucchetti Dipartimento di Economia Università Politecnica delle Marche r.lucchetti(a)univpm.it http://www.econ.univpm.it/lucchetti _______________________________________________ Gretl-users mailing list Gretl-users(a)lists.wfu.edu http://lists.wfu.edu/mailman/listinfo/gretl-users