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Re: st: Rolling regression based on trading days


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Rolling regression based on trading days
Date   Mon, 29 Apr 2013 09:42:14 +0100

Your -date- variable varies between 0 and 8399. That can't be a daily
date variable that includes dates like 31 Dec 2012.

. di %d 8399
30dec1982

. di %d 0
01jan1960

So what you are showing us? You are -list-ing something; what is it?

I also asked for -describe date-.
Nick
njcoxstata@gmail.com


On 29 April 2013 09:25, Bernice Mi <bernicem0708@gmail.com> wrote:
> Many thanks for your prompt reply Nick. Although delta is .001
> seconds, when I run rolling regression, it is still based on calendar
> days (not trading days as I want).
>
> The partial results are below. I really appreciate your help!
> 864761. | 26nov2012 |
> 864762. | 27nov2012 |
> 864763. | 28nov2012 |
> 864764. | 29nov2012 |
> 864765. | 30nov2012 |
>         |-----------|
> 864766. | 03dec2012 |
> 864767. | 04dec2012 |
> 864768. | 05dec2012 |
> 864769. | 06dec2012 |
> 864770. | 07dec2012 |
>         |-----------|
> 864771. | 10dec2012 |
> 864772. | 11dec2012 |
> 864773. | 12dec2012 |
> 864774. | 13dec2012 |
> 864775. | 14dec2012 |
>         |-----------|
> 864776. | 17dec2012 |
> 864777. | 18dec2012 |
> 864778. | 19dec2012 |
> 864779. | 20dec2012 |
> 864780. | 21dec2012 |
>         |-----------|
> 864781. | 24dec2012 |
> 864782. | 26dec2012 |
> 864783. | 27dec2012 |
> 864784. | 28dec2012 |
> 864785. | 31dec2012 |
>         +-----------+
>
> .
> end of do-file
>
> . do "C:\Users\lmi\AppData\Local\Temp\STD02000000.tmp"
>
> . su date
>
>     Variable |       Obs        Mean    Std. Dev.       Min        Max
> -------------+--------------------------------------------------------
>         date |    864785    4144.932    2229.524          0       8399
>
> .
>
> On Mon, Apr 29, 2013 at 6:16 PM, Nick Cox <njcoxstata@gmail.com> wrote:
>> It seems that you have daily data. So why does -xtset- report milliseconds?
>>
>> Show us the results of say
>>
>> . describe date
>> . su date
>> . list date in 1/5
>>
>> I don't know offhand whether -rolling- is smart about business
>> calendars. Introducing business calendars is an on-going project for
>> StataCorp and I don't have access to Stata 12 right now.
>>
>> But if Stata thinks your time variable is clock time in ms, it won't
>> be paying much attention to business calendars. As far as it is
>> concerned you have in total about 1 second's worth of data.
>>
>> Nick
>> njcoxstata@gmail.com
>>
>>
>> On 29 April 2013 08:53, Bernice Mi <bernicem0708@gmail.com> wrote:
>>> Hi All,
>>>
>>> I have an unbalanced panel data with the dates being trading days. I
>>> have already defined and formatted (using %tbcalname) the dates as
>>> business calendar. I checked by testing the lead and lag days - it
>>> worked. However, when I xtset company date, it shows that delta is
>>> 0.001 seconds. Moreover, when I run rolling regression for 3 years, it
>>> turns up to be 1035 (roughly 360*3) replications not around 780 (i.e.
>>> 260*3) replications.
>>>
>>> I am new user of Stata and could not figure out where I went wrong.
>>> Please help me.
>>>
>>> Many thanks!!
>>>
>>> Bernice
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