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Re: AW: st: Programming stata using egen functions


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: AW: st: Programming stata using egen functions
Date   Wed, 29 Apr 2009 08:40:34 +0000 (GMT)

Sounds to me like you can avoid loops by making clever use of 
-reshape- and -by-, see their helpfiles.

-- Maarten

-----------------------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


--- On Tue, 28/4/09, Anne Resende <A.C.C.Resende@rhul.ac.uk> wrote:

> From: Anne Resende <A.C.C.Resende@rhul.ac.uk>
> Subject: Re: AW: st: Programming stata using egen functions
> To: statalist@hsphsun2.harvard.edu
> Date: Tuesday, 28 April, 2009, 8:48 PM
> I swear that this is my last email:
> I trying to calculate bounds on E[y(t)].  So I need to
> calculate the 
> lower bound and also a confidence interval on it using
> boostrap.
> So I am trying to calculate:  
>                     (1)	                        (2)
> SUM    max( E[y|z=s] + max
> {(E[y|z=s']-E[u|z=u]/(s'-u))*(t-s')}) 
> (s>=t)  (s'|s>=s'>=t}    {u|u<t}
> 
> 
> (Okumura and Usui, 2006 pag.4).  So here we have s,s’,t
> and u: every 
> letter goes from 8 to 20. I decide to do a program for
> each, 
> t=8,...,20. (So I am trying to calculate the lower bound
> for each t). I 
> also have tried to use all of t together (also create
> forvalues for t) 
> but stata gives a message “No room to add more
> variables”.  In the 
> program that I already sent to you I am considering that t
> is equal 9, 
> so u=8 because u<9  (I do this in line 7 : qui sum
> `1' if u==8 ). So I 
> have tried to use rowmax() to calculate the maximum of the
> first max 
> parenthesis (lines 9 and 11- part (1) + (2)), doesn’t 
> matter if I 
> calculate (2) and take the max or sum (1) and (2) and take
> the max, as 
> I have to take the max again). Then in the reminding lines
> I have tried 
> to multiply  (3) {(1)+(2)}, the whole equation by P(z=s)
> and then use 
> rowtotal to sum all of these observations, as  I have to
> sum over s>=t. 
> (lines 15 and 16 of the programe)
> 
> I am afraid that this could be less clear than before but
> is exactly 
> what I trying to do.  Of course that I do not expect you
> create an ado 
> file for me. I just want some tips or some help as you all
> know much 
> more about stata programming. So I really need to move the
> calculation 
> of the maximum outside the loop? 
> 
> 
> Many thanks 
> 
> 
> 
> 
> Nick Cox wrote:
> 
> 
> >Quite so, and not a problem. It's my point 1 that
> is more important. 
> >
> >Nick 
> >n.j.cox@durham.ac.uk 
> >
> >
> >-----Original Message-----
> >From: Anne Resende [mailto:A.C.C.Resende@rhul.ac.uk] 
> >Sent: 28 April 2009 19:02
> >To: Nick Cox
> >Subject: RE: st: Programming stata using egen functions
> >
> >
> >2. "You don't know enough Stata to do what you
> want without help."
> >That is why I decided to send an email to statalist. 
> >Thanks anyway
> >Anne 
> >
> >
> >
> 
> 
> Martin Weiss wrote:
> 
> 
> >
> ><> 
> >
> >True, I was too focused on the issue with the -scalar-
> and -local- 
> problem to notice that -rowtotal()- was not the best
> example.
> >
> >Overall, I am sensing an overwhelming willingness to
> help Anne, but she 
> should try to describe _verbally_ what she wants to
> achieve, and I am 
> sure no more than a couple of lines will be necessary to
> get there. 
> Maarten has already had a stab at it...
> >
> >
> >HTH
> >Martin
> >
> >
> >-----Ursprüngliche Nachricht-----
> >Von: owner-statalist@hsphsun2.harvard.edu 
> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag
> von Nick Cox
> >Gesendet: Dienstag, 28. April 2009 19:43
> >An: statalist@hsphsun2.harvard.edu
> >Betreff: RE: st: Programming stata using egen functions
> >
> >But then the -rowtotal()- is pointless. As Kit pointed
> out several 
> posts ago, the row total of one item is precisely that
> item. 
> >
> >Nick 
> >n.j.cox@durham.ac.uk 
> >
> >Martin Weiss
> >
> >Better example
> >
> >*************
> >tempvar ep_`s'
> >gen `ep_`s''=exem2_`s'*`P1_`s'' 
> >qui egen `ep2_`s''=rowtotal(`ep_`s'')
> >*************
> >
> >Martin Weiss
> >
> >" So in line 9 I substitute `scalar’ for
> `local’ hoping 
> >that rowmax() could now recognize the varlist."
> >
> >Well, you have not passed a -varlist- to -egen,
> rowmax()- so it 
> complains about its syntax statement not being respected,
> and rightly 
> so. -local-s and -scalar-s are equally bad, in this
> respect. If that is 
> all that is standing between you and success, then let the
> -gen- and 
> -egen- statements refer to -tempvar-s. In this fashion, at
> least they 
> will be legal...
> >
> >
> >So instead of
> >
> >**
> >qui summarize `1' if `sp'==u
> >local mean1_`s'`sp' =r(mean)
> >**
> >
> >say -egen mean1_ssp=mean(`1') if `sp'==u-
> >
> >Anne Resende
> >
> >Thanks a lot for all answers!!
> >Just to clarify some points:
> >I understood that the egen functions rowmax() and
> rowtotal() did not 
> >accept scalar. So in line 9 I substitute `scalar’ for
> `local’ hoping 
> >that rowmax() could now recognize the varlist. But
> stata returns de 
> >same error message. I need the rowmax() function to
> returns the maximum 
> >values between the varilist. (the maximum values within
> each `s’)
> >
> >So I have tried:
> >program mymean, rclass
> >  1.   syntax [varlist] [if]
> >  2.   tokenize "`varlist'"
> >  3.   forvalues s=9(1)20 {
> >  4.   forvalues sp=9(1)`s' {
> >  5.         qui summarize `1' if `sp'==u
> >  6.         local mean1_`s'`sp' =r(mean)
> >  7.         qui sum `1' if u==8
> >  8.         local mean2_`s'`sp' =r(mean)
> >  9.           local
> m_`s'`sp'=`mean1_`s'`sp'' +
> ((`mean1_`s'`sp'' - 
> >`mean2_`s'`sp'')/(`sp'-8))*(9-`sp')
>    
> > 10.         tempvar exem_`s' P_`s' ep_`s'
> ep2_`s'
> > 11.        qui egen
> `exem_`s''=rowmax(m_`s'`sp')       
> > 12.        qui gen `P_`s''=sum(P) if
> `s'==u & id==1
> > 13.        qui sum `P_`s'', meanonly
> > 14.        local P1_`s'=r(max)
> > 15.          scalar
> ep_`s'=exem2_`s'*`P1_`s'' 
> > 16.        qui egen
> `ep2_`s''=rowtotal(ep_`s')
> > 17.          return scalar eq2=`ep2_`s''    
> > 18. }
> > 19. }
> > 20. end
> >
> >end of do-file
> >. mymean loghw
> >variable m_99 not found
> >r(111);
> >
> >1) I understand the differences between egen sum( )and
> stata fuctions 
> >sum(), but neither gives me what I need. I intend to
> use rowtotal() 
> >because it sums the observations on the rows not on the
> columns as egen 
> >sum() and sum() do.
> >
> >2) Sorry about:  return scalar
> eq29=rowtotal(ep_`s') that I wrote in 
> >the other email.. I know that it’s wrong
> >
> >3)What is my aim? As I told I need to end up with one
> variable in order 
> >to run the bootstrap. 
> >I want to the create the program mymean and then run:
> bootstrap r(eq2), 
> >reps(#) seed(#)  : mymean loghw  (I am following the
> idea on: 
> >http://www.stata.com/capabilities/boot.html)
> >
> >4)I think that I cannot use a do.file because I will
> end up with a 
> >constant (I also tried) and so I could not run the
> bootstrap. Creating 
> >and ado file the program allows me to use the boots
> after.
> >
> >So all I want to do is to write a program to calculate
> my statistics of 
> >interest and then apply the bootstrap. And my problem
> is how I can 
> >construct a varlist in order to run my program using
> rowmax() and 
> >rowtotal(). Or maybe there is another way to do that
> without having to 
> >use rowmax() and rowtotal() functions.
> >I hope that is clearer now,
> >Thanks 
> >Anne
> >
> >Thanks
> >Anne
> >
> >
> >Richard Ochmann wrote:
> >
> >
> >>...
> >>not entirely clear what you want to do there,
> >>but maybe you can borrow from this code on
> generating a list of scalars 
> >>(which might be inefficient either):
> >>
> >>***
> >>#delimit;
> >>sysuse auto;
> >>local meanlist = "0";
> >>forvalues i = 1/2       {;
> >>forvalues j = `i'/3     {;
> >>quietly sum price, meanonly;
> >>scalar s`i'`j' = r(mean)/runiform();
> >>local meanlist = " `meanlist',
> `=s`i'`j'' ";
> >>di "`meanlist'";
> >>scalar mymax = max(`meanlist');
> >>di mymax;
> >>                                                };
> >>                                        };
> >>***
> >>
> >>best, rich
> >>
> >>
> >>owner-statalist@hsphsun2.harvard.edu schrieb am
> 28.04.2009 02:05:25:
> >>
> >>> Dear All
> >>> I am having some problems with my ado.file
> whenever I try to include 
> >>> some egen functions like rowmax and rowtotal.
> I am currently using 
> >>> Stata 10.0
> >>> 
> >>> My ado program is:
> >>> 
> >>>  program mymean, rclass
> >>>   1.   syntax [varlist] [if]
> >>>   2.   tokenize "`varlist'"
> >>>   3.   forvalues s=9(1)20 {
> >>>   4.   forvalues sp=9(1)`s' {
> >>>   5.         qui summarize `1' if
> `sp'==u
> >>>   6.         local mean1_`s'`sp'
> =r(mean)
> >>>   7.         qui sum `1' if u==8
> >>>   8.         local mean2_`s'`sp'
> =r(mean)
> >>>   9.           scalar
> m_`s'`sp'=`mean1_`s'`sp'' +
> ((`mean1_`s'`sp'' - 
> >>>
> `mean2_`s'`sp'')/(`sp'-8))*(9-`sp')
> >>>  10.         tempvar exem_`s' P1_`s'
> P_`s' ep_`s' ep2_`s'
> >>>  11.         qui egen
> `exem_`s''=max(m_`s'`sp')
> >>>  12.           return scalar
> exem2_`s'=`exem_`s''*1
> >>>  13.           qui gen `P1_`s''=sum(P)
> if `s'==u & id==1
> >>>  14.           qui egen `P_`s''
> =max(`P1_`s'') 
> >>>  15.           scalar
> ep_`s'=exem2_`s'*`P_`s'' 
> >>>  16.         qui gen
> `ep_`s''=exem2_`s'*`P_`s''
> >>>  17.         return scalar
> eq29=sum(ep_`s')
> >>>  18. }
> >>>  19. }
> >>>  20. end
> >>> This program is running well. But in lines 11
> and 17, I in fact need 
> >to 
> >>> use the commands rowmax rather than max and
> rowtotal rather sum. So 
> >>> when I use max and sum the program runs well
> but when I substitute 
> >this 
> >>> commands whith rowmax and rowtotal stata gives
> me the following error 
> >>> message after I typed mymean loghw: 
> >>> 
> >>> 
> >>>  program mymean, rclass
> >>>   1.   syntax [varlist] [if]
> >>>   2.   tokenize "`varlist'"
> >>>   3.   forvalues s=9(1)20 {
> >>>   4.   forvalues sp=9(1)`s' {
> >>>   5.         qui summarize `1' if
> `sp'==u
> >>>   6.         local mean1_`s'`sp'
> =r(mean)
> >>>   7.         qui sum `1' if u==8
> >>>   8.         local mean2_`s'`sp'
> =r(mean)
> >>>   9.           scalar
> m_`s'`sp'=`mean1_`s'`sp'' +
> ((`mean1_`s'`sp'' - 
> >>>
> `mean2_`s'`sp'')/(`sp'-8))*(9-`sp')
> >>>  10.         tempvar exem_`s' P1_`s'
> P_`s' ep_`s' ep2_`s'
> >>>  11.         qui egen
> `exem_`s''=rowmax(m_`s'`sp')
> >>>  12.           return scalar
> exem2_`s'=`exem_`s''*1
> >>>  13.           qui gen `P1_`s''=sum(P)
> if `s'==u & id==1
> >>>  14.           qui egen `P_`s''
> =max(`P1_`s'') 
> >>>  15.           scalar
> ep_`s'=exem2_`s'*`P_`s'' 
> >>>  16.         qui gen
> `ep_`s''=exem2_`s'*`P_`s''
> >>>  17.         return scalar
> eq29=rowtotal(ep_`s')
> >>>  18. }
> >>>  19. }
> >>>  20. end
> >>> . 
> >>> end of do-file
> >>> . mymean loghw
> >>> variable m_99 not found
> >>> r(111);
> >>> 
> >>> So I would like to know why the program
> recognizes the max and sum 
> >egen 
> >>> functions but do not recognize (or do not find
> my variable) when I use 
> >>> the rowmax and rowtotal egen functions. Is
> there any programming 
> >>> differences between these two kind of egen
> functons?
> >
> >*
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> >
> >
> >*
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> >
> 
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