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Re: st: Re: Analyzing time series data on prices by districts & markets
From
Chris Parker <[email protected]>
To
[email protected]
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 [email protected]
On Tue, Jun 14, 2011 at 7:54 AM, Partho Sarkar <[email protected]> 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
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