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Re: Re: st: RE: AW: ratio function


From   Steve Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: Re: st: RE: AW: ratio function
Date   Tue, 27 Apr 2010 09:08:33 -0400

""n addition, -suest- is not necessary after -mean, over()-, because
> all the results are already available to -nlcom-.

I've already shown the syntax when a single mean is requested, but
with multiple means it is a little different:

********
 sysuse auto,clear
 svyset _n
 svy: mean mpg, over(foreign)   //one variable
 nlcom _b[Foreign]/_b[Domestic]
 nlcom [mpg]Foreign/[mpg]Domestic  //same

 svy:  mean mpg trunk, over(foreign)   //two variables
 nlcom [mpg]Foreign/[mpg]Domestic  - [trunk]Foreign/[trunk]Domestic

***************************************************

>

On Tue, Apr 27, 2010 at 7:37 AM, Steve Samuels <sjsamuels@gmail.com> wrote:
> Sorry, I don't have version 10, but use Martin's trick
> *************
> suest, coefl
> *************
> to see what Stata does call these in Version 10.  In Version 11 both
> syntaxes work.
>
> Why your errors?  I don't have Verstion 10,  but my guess is that it's
> because -mean- and -svy: mean- are not regression commands.  They will
> take multiple variables, so there  is no "constant".
>
> ****************
> sysuse auto, clear
> svy: mean mpg weight
> di _b[mpg] _b[weight]
>
> -suest- only works  with commands for which -predict- is a valid
> post-estimation command. (See the -help-)  That's not true of -mean-
> or -svy: mean-That's probably the source of the error message, at
> least indirectly.
>
> In addition, -suest- is not necessary after -mean, over()-, because
> all the results are already available to -nlcom-.
>
> Steve
>
> 2010/4/27 Roman Kasal <kasal@trexima.cz>:
>> "nlcom  _b[y2008:_cons]/_b[y2009:_cons]" really don't work for me (STATA 10.1)  but "nlcom [y2008]_cons/[y2009]_cons" does
>>
>> btw, don't you know why this code ends with an error?
>>
>> ********************
>> est drop _all
>> svyset ICO [pw=vahaHMM], strata(stk2) fpc(fpc1) singleunit(centered)
>> svy: mean hrMzdaMes if rok==2009
>> est sto r2009
>> svy: mean hrMzdaMes if rok==2008
>> est sto r2008
>> est dir
>>
>> -------------------------------------------------------
>>        name | command      depvar       npar  title
>> -------------+-----------------------------------------
>>       r2009 | mean         no depvar       1
>>       r2008 | mean         no depvar       1
>> -------------------------------------------------------
>> suest r2009 r2008
>> impossible to retrieve e(b) and e(V) in r2009
>> ****************
>>
>> And does suest handle with "svy:mean x, over(y)"?
>>
>>
>>
>> -----Original Message-----
>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steve Samuels
>> Sent: Monday, April 26, 2010 2:17 PM
>> To: statalist@hsphsun2.harvard.edu
>> Subject: Re: Re: st: RE: AW: ratio function
>>
>> You're very welcome. Either syntax works. See section 13.5 of the User's Guide.
>>
>> Steve
>>
>> 2010/4/26 Roman Kasal <kasal@trexima.cz>:
>>> thank you, it helps a lot!
>>>
>>> just small correction:
>>>
>>> the last command should by "nlcom [y2008]_cons/[y2009]_cons" I assume
>>>
>>> roman
>>>
>>> -----Original Message-----
>>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steve Samuels
>>> Sent: Monday, April 26, 2010 1:23 AM
>>> To: statalist@hsphsun2.harvard.edu
>>> Subject: Re: Re: st: RE: AW: ratio function
>>>
>>> My previous example was flawed, Because males and females could be
>>> present in the same PSU (famid), the degrees of freedom for -suest-
>>> did not equal the sum of the d.f. for the separate regressions.  Here
>>> is another  example with proper strata. Note that the degrees now add
>>> properly.
>>> Steve
>>>
>>> *************************
>>> webuse income, clear
>>> gen  year = 2008 + (famid>68)
>>> tab year
>>> svyset famid, strata(year)
>>> svy: reg inc if year==2008
>>> estimates store y2008
>>> svy: reg inc if year==2009
>>> estimates store y2009
>>> suest y2008 y2009
>>> matrix list e(V)   //results from different years are independent
>>> nlcom  _b[y2008:_cons]/_b[y2009:_cons]
>>> ***********************************************
>>> On Fri, Apr 23, 2010 at 10:40 AM, Steve Samuels <sjsamuels@gmail.com> wrote:
>>>> Just use -suest-.  Use the fact that -reg- without an argument is
>>>> equivalent to estimating the mean.
>>>>
>>>> ********************
>>>> webuse income, clear
>>>> svyset famid
>>>> svy: reg inc if male
>>>> estimates store Male
>>>> svy: reg inc if !male
>>>> estimates store Female
>>>> suest Male Female
>>>> nlcom _b[Male:_cons]/_b[Female:_cons]
>>>> *************************
>>>> Steve
>>>>
>>>> 2010/4/23 Roman Kasal <kasal@trexima.cz>:
>>>>> yes, the year is another survey (different time; the years cannot be pooled because of degrees of freedom) and is included in strata.
>>>>>
>>>>> so there is no solution for this case? just manually?
>>>>>
>>>>> -----Original Message-----
>>>>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steve Samuels
>>>>> Sent: Friday, April 23, 2010 1:32 PM
>>>>> To: statalist@hsphsun2.harvard.edu
>>>>> Subject: Re: Re: st: RE: AW: ratio function
>>>>>
>>>>>> "svy: mean wage, over(year)" is not equal "svy: mean wage if year==2009"
>>>>>
>>>>> The "if statement" is incorrect, unless year was a stratification
>>>>> variable that you identified to Stata.
>>>>>
>>>>> -nlcom- after -svy: mean-, over(year),   is the proper approach.
>>>>>
>>>>>
>>>>> 2010/4/23 Roman Kasal <kasal@trexima.cz>:
>>>>>> ok, for this purpose I agree, that is ok...but what about if I want to calculate SE of Mean in years 2009 and 2008 and then ratio with SE of the means?
>>>>>>
>>>>>> the problem is that CI of
>>>>>> "svy: mean wage, over(year)" is not equal "svy: mean wage if year==2009"
>>>>>> for the year 2009 because of different degrees of freedom (SE's are equal), the first command gives wrong CI.
>>>>>>
>>>>>> is any elegant solution to handle this in Stata with "nlcom" or do I have to calculate it manually?
>>>>>>
>>>>>> thank you
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steve Samuels
>>>>>> Sent: Thursday, April 22, 2010 3:08 PM
>>>>>> To: statalist@hsphsun2.harvard.edu
>>>>>> Subject: Re: Re: st: RE: AW: ratio function
>>>>>>
>>>>>> The degrees of freedom are correct.  See any sampling text.
>>>>>>
>>>>>> Briefly: To identify a subpopulation, each observation in the sample
>>>>>> receives a 0-1  indicator variable d.   If X is the numerator variable
>>>>>>  and Y is the denominator variable, the numerator for the ratio of is
>>>>>> the sum *over the entire sample*  of Z_x = d *X and the denominator is
>>>>>> the sum of Z_y = d * Y.  The standard errors are based on variability
>>>>>> in the Z's, including the zero values.
>>>>>> By the way, the standard errors formulas are valid only if the
>>>>>> expected number of observations in a subpopulation is at least 20.
>>>>>>
>>>>>> Steve
>>>>>>
>>>>>> 2010/4/22 Roman Kasal <kasal@trexima.cz>:
>>>>>>> thank you for the code, but I have found a problem:
>>>>>>>
>>>>>>> if I calculate over(foreign) the bound are enumerated with "e(N_psu)-e(N_strata)" degrees of freedom, but not for each foreign (degrees of freedom are for whole dataset) and this is wrong I assume.
>>>>>>>
>>>>>>> thank you
>>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steve Samuels
>>>>>>> Sent: Friday, April 02, 2010 2:58 PM
>>>>>>> To: statalist@hsphsun2.harvard.edu
>>>>>>> Subject: Re: Re: st: RE: AW: ratio function
>>>>>>>
>>>>>>> Roman
>>>>>>> Perhaps we misunderstand what you are asking for. I  We have been
>>>>>>> assuming that you  want the ratio of the means of two variables
>>>>>>> ("columns"?) measured possibly on the same person.  Perhaps you want
>>>>>>> the ratio of the means of one variable for two subpopulations.   Both
>>>>>>> analyses will ignore missing values.
>>>>>>>
>>>>>>> If this is not what you desire, then please demonstrate by hand what
>>>>>>> you do want on a small, non-survey data set.. Also I'd like to know
>>>>>>> which R function does what are asking for
>>>>>>>
>>>>>>>  The following do file computes the ratio of means with CI and then
>>>>>>> does the same for the log ratio and transforms to the original scale.
>>>>>>>
>>>>>>> -Steve
>>>>>>>
>>>>>>>
>>>>>>> **************************CODE BEGINS**************************
>>>>>>> capture program drop _all
>>>>>>> program antilog
>>>>>>> local lparm  el(r(b),1,1)
>>>>>>> local se    sqrt(el(r(V),1,1))
>>>>>>> local bound  invttail(e(df_r),.025)*`se'
>>>>>>> local parm  exp(`lparm')
>>>>>>> local ll  exp(`lparm'  - `bound')
>>>>>>> local ul  exp( `lparm' + `bound')
>>>>>>> di  "parm =" `parm'  "    ll = " `ll'  "   ul = " `ul'
>>>>>>> end
>>>>>>>
>>>>>>> sysuse auto, clear
>>>>>>> svyset _n
>>>>>>> svy: mean mpg, over(foreign)
>>>>>>> nlcom (myratio1: _b[Domestic]/_b[Foreign])   //ratio
>>>>>>> nlcom (myratio2: log(_b[Domestic]/_b[Foreign]))   // log ratio
>>>>>>> // Confidence interval of last -nlcom- on antilog scale
>>>>>>> antilog
>>>>>>> ***************************CODE ENDS***************************
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> .
>>>>>>>
>>>>>>> On Fri, Apr 2, 2010 at 2:37 AM, Roman Kasal <kasal@trexima.cz> wrote:
>>>>>>>> I don't agree...so how to do it when you want to find out ratio between
>>>>>>>> years, male X female, ...? So there is no solution? Just to keep N,mean,
>>>>>>>> SE, degrees of freedom, N_strata, N_psu, .... and calculate it manually?
>>>>>>>> I think it is not appropriate solution, at least to have it as an
>>>>>>>> option. I think there is missing a lot with complex survey in Stata and
>>>>>>>> complex survey is needed for almost every survey research, even freeware
>>>>>>>> R-project is better equipped :(
>>>>>>>>
>>>>>>>> so have a hope Stata will get it soon....immediately we are buying it
>>>>>>>> again :)
>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>> And it should.   Data (x,y) (1,2) (2,4) (3,6) (100,.)    will give an
>>>>>>>> entirely different view of the data if the unpaired observation is
>>>>>>>> included in a mean or ratio calculation.  Or consider data with x
>>>>>>>> missing in half the pairs and y missing in the other half; the ratio
>>>>>>>> of means would be meaningless.
>>>>>>>>
>>>>>>>> The formulas for standard errors for ratios  assume that the data are
>>>>>>>> paired. Formally, they are based on the residual MSE of a regression
>>>>>>>> of y on x through the origin. You cannot do that regression with
>>>>>>>> unpaired data.
>>>>>>>>
>>>>>>>> If your concern is missing data, the solution is to impute the missing
>>>>>>>> values before analysis.
>>>>>>>>
>>>>>>>> Steve
>>>>>>>>
>>>>>>>>
>>>>>>>> *
>>>>>>>> *   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/
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Steven Samuels
>>>>>>> sjsamuels@gmail.com
>>>>>>> 18 Cantine's Island
>>>>>>> Saugerties NY 12477
>>>>>>> USA
>>>>>>> Voice: 845-246-0774
>>>>>>> Fax:    206-202-4783
>>>>>>>
>>>>>>> *
>>>>>>> *   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/
>>>>>>>
>>>>>>> *
>>>>>>> *   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/
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Steven Samuels
>>>>>> sjsamuels@gmail.com
>>>>>> 18 Cantine's Island
>>>>>> Saugerties NY 12477
>>>>>> USA
>>>>>> Voice: 845-246-0774
>>>>>> Fax:    206-202-4783
>>>>>>
>>>>>> *
>>>>>> *   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/
>>>>>>
>>>>>> *
>>>>>> *   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/
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Steven Samuels
>>>>> sjsamuels@gmail.com
>>>>> 18 Cantine's Island
>>>>> Saugerties NY 12477
>>>>> USA
>>>>> Voice: 845-246-0774
>>>>> Fax:    206-202-4783
>>>>>
>>>>> *
>>>>> *   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/
>>>>>
>>>>> *
>>>>> *   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/
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Steven Samuels
>>>> sjsamuels@gmail.com
>>>> 18 Cantine's Island
>>>> Saugerties NY 12477
>>>> USA
>>>> Voice: 845-246-0774
>>>> Fax:    206-202-4783
>>>>
>>>
>>>
>>>
>>> --
>>> Steven Samuels
>>> sjsamuels@gmail.com
>>> 18 Cantine's Island
>>> Saugerties NY 12477
>>> USA
>>> Voice: 845-246-0774
>>> Fax:    206-202-4783
>>>
>>> *
>>> *   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/
>>>
>>> *
>>> *   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/
>>>
>>
>>
>>
>> --
>> Steven Samuels
>> sjsamuels@gmail.com
>> 18 Cantine's Island
>> Saugerties NY 12477
>> USA
>> Voice: 845-246-0774
>> Fax:    206-202-4783
>>
>> *
>> *   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/
>>
>> *
>> *   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/
>>
>
>
>
> --
> Steven Samuels
> sjsamuels@gmail.com
> 18 Cantine's Island
> Saugerties NY 12477
> USA
> Voice: 845-246-0774
> Fax:    206-202-4783
>



-- 
Steven Samuels
sjsamuels@gmail.com
18 Cantine's Island
Saugerties NY 12477
USA
Voice: 845-246-0774
Fax:    206-202-4783

*
*   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/


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