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Re: Manipulating a database (Riccardo (Jack) Lucchetti) From: Leandro Zipitria <leandro.zipitria(a)gmail.com&gt; Date: April 2, 2010 11:31:12 PM MDT To: Gretl list <gretl-users(a)lists.wfu.edu&gt; Cc: Fernando Borraz <fborraz(a)gmail.com&gt; Subject: [Gretl-users] Manipulating a database Reply-To: Gretl list <gretl-users(a)lists.wfu.edu&gt; 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. Thank in advance. Best regards, Leandro Zipitría <gretl.xls> From: "Riccardo (Jack) Lucchetti" <r.lucchetti(a)univpm.it&gt; Date: April 3, 2010 2:33:03 AM MDT To: Gretl list <gretl-users(a)lists.wfu.edu&gt; Cc: Fernando Borraz <fborraz(a)gmail.com&gt; Subject: Re: [Gretl-users] Manipulating a database Reply-To: r.lucchetti(a)univpm.it, Gretl list <gretl-users(a)lists.wfu.edu&gt; 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