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From | Chris Parker <cparker.phd2007@london.edu> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: Re: Analyzing time series data on prices by districts & markets |
Date | Tue, 14 Jun 2011 09:20:40 +0100 |
Hi Partho, Yes - the second and third parts are both calculated incorrectly. The issue is that -egen, tag- only tags one instance of a district. On a given date the "tagged" observation may or may not be considered. This should give you the correct results. egen districttag = tag(district) bysort state: egen numdistricts = total(districttag) egen districtdatetag = tag(district date) bysort state date: egen districtswithprices = total(districtdatetag) gen percentdistrictswithprices = districtswithprices/numdistricts egen statetag = tag(state) egen numstates = total(statetag) egen statedatetag = tag(state date) bysort date: egen stateswithprices = total(statedatetag) gen percentstateswithprices = stateswithprices/numstates Sorry for sending you down the wrong path before! Chris Chris Parker ________________________________ PhD Candidate | Management Science & Operations London Business School | Regent's Park | London NW1 4SA | United Kingdom Direct line +44 (0)20 7000 8816 | Email cparker.phd2007@london.edu On Tue, Jun 14, 2011 at 7:54 AM, Partho Sarkar <partho.ss@gmail.com> wrote: > > Hello Chris, > > The code worked fine, except for this section: > > The number of districts in each state for which prices are > reported, versus the total no. of districts in that state > > egen districttag = tag(district) > bysort state: egen numdistricts = total(districttag) > bysort state date: egen districtswithprices = total(districttag) > gen percentdistrictswithprices = districtswithprices/numdistricts > > I am getting many false zero values for districtswithprices, as seen > in this extract from the output: > > The headers for the 7 columns: reportdate state mandi > district mandisopen numdistricts districtswithprices > > 06/01/09 Andhra Addank Prakas 3 8 6 > 06/01/09 Andhra Bhimav West G 2 8 6 > 06/01/09 Andhra Kothav Vizian 2 8 6 > 06/02/09 Andhra Atmaku Kurnoo 1 8 0 > 06/02/09 Andhra Kondap Prakas 2 8 0 > 06/02/09 Andhra Satten Guntur 1 8 0 > > > Clearly, if mandisopen>0, districtswithprices =0 can't be right. > Wonder if you can spot the problem with the code without too much more > trouble. > > And thank you, Dr. Cox- I had a glance at the article, and will go > through it carefully- it looks quite insightful. > > Regards, > > Partho > > Partha S. Sarkar > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > > ______________________________________________________________________ > > This email has been scanned by the MessageLabs Email Security System > on behalf of the London Business School community. > For more information please visit http://www.messagelabs.com/email > ______________________________________________________________________ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/