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

[Steve Samuels <sjsamuels@gmail.com>]

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:
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>> *   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

*
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