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Re: st: Routine from do-file that every time it's run gives a different result


From   Roberto Ferrer <[email protected]>
To   Stata Help <[email protected]>
Subject   Re: st: Routine from do-file that every time it's run gives a different result
Date   Wed, 6 Nov 2013 17:27:23 -0430

Clarice,

Google this and read it. It is important.

The Stata Journal (2006)
6, Number 1, pp. 144–146
Stata tip 28: Precise control of dataset sort order
L. Philip Schumm

On Wed, Nov 6, 2013 at 5:20 PM, Nick Cox <[email protected]> wrote:
> But that solves the problem with the price of not understanding it.
> Somewhere Clarice has hidden assumptions about the -sort- order being
> enough to get the right order without extra information that are not
> correct.
> Nick
> [email protected]
>
>
> On 6 November 2013 21:46, Sergiy Radyakin <[email protected]> wrote:
>> Clarice, add the option stable to the sort commands. Without this
>> option, the -sort- command will break the ties randomly. See here:
>> http://www.stata.com/help.cgi?sort
>>
>> Best, Sergiy
>>
>> On Wed, Nov 6, 2013 at 4:30 PM, Clarice Martins
>> <[email protected]> wrote:
>>> Dear Statalist group,
>>>
>>> I have a routine that apparently was running ok, and then I noticed that everytime I execute the code I get different results for one of the variables.
>>> (The routine is long, so I don't know how to best provide you guys with enough info.)
>>>
>>> 1) I believe the problem has to do with variable -P5- since this is the variable which average changes every time I run the code.
>>>
>>> 2) Sample of the results, I am getting:  as you can see variable P1 is always approximately the same (it should be the same) and variable Strategy is ALWAYS the same, but var -P5- changes by a lot. (I've shown two outputs, but I've ran it several, several times.)
>>>
>>>
>>> . esttab .
>>>
>>> ----------------------------
>>>                       (1)
>>>                      Mean
>>> ----------------------------
>>> P1                  0.300***
>>>                    (3.41)
>>>
>>> P5                  6.154
>>>                    (1.53)
>>>
>>> strategy            7.190
>>>                    (1.78)
>>> ----------------------------
>>> N                     150
>>> ----------------------------
>>>
>>>
>>> ----------------------------
>>>                       (1)
>>>                      Mean
>>> ----------------------------
>>> P1                  0.223*
>>>                    (2.24)
>>>
>>> P5                  3.286
>>>                    (1.15)
>>>
>>> strategy            7.190
>>>                    (1.78)
>>> ----------------------------
>>> N                     150
>>> ----------------------------
>>>
>>> 3) Piece of the code that deals with creating and changing variable P5: (my apologies if this is confusing or too long)
>>>
>>> ***create variable P1/P5 and sum all 1st/5th quintiles per <yrmonth>
>>> gen P1_sell = .
>>> quietly levelsof yrmonth, local(levs)
>>> quietly foreach lev of local levs {
>>>         egen work=total(return) if rtype=="buy_sell_period" & yrmonth == "`lev'" & quintile==1
>>>         replace P1_sell=work if rtype=="buy_sell_period" & yrmonth == "`lev'" & quintile==1
>>>         drop work
>>> }
>>>
>>> gen P5_buy = .
>>> quietly levelsof yrmonth, local(levs)
>>> quietly foreach lev of local levs {
>>>         egen work=total(return) if rtype=="buy_sell_period" & yrmonth == "`lev'" & quintile==5
>>>         replace P5_buy=work if rtype=="buy_sell_period" & yrmonth == "`lev'" & quintile==5
>>>         drop work
>>> }
>>>
>>> sort quintile yrmonth rtype
>>>
>>> **undo the buy/sell operation
>>> *in order to do the procedure, first copy quintile #s to same <co_id> but for 6 <yrmonth> LATER
>>>
>>> bysort co_id period: egen tocopy2 = total(quintile / (rtype == "buy_sell_period"))
>>> bysort co_id rtype (negperiod) : replace quintile = tocopy2[_n+6] if missing(quintile) & rtype == "hold_period"
>>> sort quintile yrmonth rtype
>>>
>>> *add sums of 1st/5th quintiles for <hold_period> to variables P1/P5
>>>
>>> quietly levelsof yrmonth, local(levs)
>>> quietly foreach lev of local levs {
>>>         egen work=total(return) if rtype=="hold_period" & yrmonth == "`lev'" & quintile==5
>>>         replace P1_sell=work if rtype=="hold_period" & yrmonth == "`lev'" & quintile==5
>>>         drop work
>>> }
>>>
>>> quietly levelsof yrmonth, local(levs)
>>> quietly foreach lev of local levs {
>>>         egen work=total(return) if rtype=="hold_period" & yrmonth == "`lev'" & quintile==1
>>>         replace P5_buy=work if rtype=="hold_period" & yrmonth == "`lev'" & quintile==1
>>>         drop work
>>> }
>>> sort quintile yrmonth rtype
>>>
>>>
>>> ***------procedures for Strategy analysis
>>> **preparing time-series
>>> *P1 is the variable to use for the time-series / keep -P1_sell- intact just for the sake of it
>>>
>>> gen P1 = P1_sell
>>> gen copyP1=P1
>>> replace P1 = . if P1 == copyP1[_n-1]
>>> drop copyP1
>>>
>>> *P5 is the variable to use for the time-series / keep -P5_buy- intact just for the sake of it
>>>
>>> gen P5 = P5_buy
>>> gen copyP5=P5
>>> replace P5 = . if P5 == copyP5[_n-1]
>>> drop copyP5
>>>
>>> *keeping only time-series variables & unique records
>>> keep P1 P5 period
>>>
>>> sort period P1 P5
>>> quietly by period P1 P5:  gen dup = cond(_N==1,0,_n)
>>> drop if dup>0
>>> drop dup
>>>
>>> sort period P1 P5
>>> gen P5copy = P5
>>> replace P5 = P5copy[_n+1] if P5 >= .
>>> replace P5 = P5copy[_n+3] if P5 >= .
>>> drop P5copy
>>>
>>> sort period
>>> quietly by period: gen dup = cond(_N==1,0,_n)
>>> drop if dup>2
>>> drop dup
>>>
>>> gen temp = P1 + P5
>>> drop if temp >= .
>>> drop temp
>>>
>>> by period: egen strategy=total(P1 + P5)
>>>
>>> sort strategy
>>> quietly by strategy: gen dup = cond(_N==1,0,_n)
>>> drop if dup>1
>>> drop dup
>>>
>>> sort period
>>>
>>> ** changing into a time-series // not sure if it is necessary yet...
>>> tsset period
>>> mean P1 P5 strategy
>>> ******end of code
>>>
>>> Thanks for your consideration! Any comment or suggestions will be appreciated.
>>> Clarice
>>>
>>>
>>> *
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>>
>> *
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>
> *
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