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Re: st: RE: Can't store estimates after logistic regression


From   Steve Samuels <sjsamuels@gmail.com>
To   Edouard Betsem <edouardbetsem@gmail.com>
Subject   Re: st: RE: Can't store estimates after logistic regression
Date   Sun, 30 Jun 2013 07:28:38 -0400

Edouard:

Please do not send me private messages asking for advice, except as the Statalist FAQ provide (i.e. for paid consultation). I'm not familiar with
the other two commands.


Steve
On Jun 30, 2013, at 2:26 AM, Edouard Betsem wrote:

Thanks, I tried both models and they are working.
I also ran a -rocreg- and -rocregplot- model that returned a p value of 0.08
The roccomp model returned a p value of 0.008

Which one should I consider here?

Edouard


On 29/06/2013 09:33, Steve Samuels wrote:
> Just a thought:
> 
> Since you have models with single classification variables,
> -logistic- isnt't strictly necessary. You can use
> -roccomp- on any set of predictors, as long as higher
> values of each are associated with higher risk of the
> event.
> 
> . corr foreign mpg
> . corr foreign turn //note negative correlation
> . gen rturn = -turn  // reverse turn
> . roccomp foreign mpg rturn
> 
> Higher values of predictions after -logistic- are always
> associated with increased risk, so no reversals
> are needed.
> 
> ---------------------------
> 
> Steve
> 
> Ed:
> 
> You probably want something like this:
> 
> . sysuse auto, clear
> . logistic foreign mpg
> . predict p1
> . logistic foreign turn
> . predict p2
> . roccomp foreign p1 p2
> 
> 
> Steve
> 
> On Jun 28, 2013, at 7:40 PM, Edouard Betsem wrote:
> 
> Thanks Steve, I understand it better now. I got to go through some more readings.
> Ed
> 
> 
> On 28/06/2013 15:54, Steve Samuels wrote:
>> Eduoard:
>> 
>> If you do
>> 
>> . des _est_mod1
>> 
>> you will see the variable label: "esample() from estimates store".
>> esample() just records whether the observation was used in the analysis
>> 
>> It  not the kind of variable needed by -roccomp-, which has syntax:
>> 
>> . rocommp refvar classvar
>> 
>> According to the Manual:
>> 
>> "The two variables refvar and classvar must be numeric. The reference
>> variable indicates the true state of the observation, such as diseased
>> and nondiseased or normal and abnormal, and must be coded as 0 and 1.
>> The rating or outcome of the diagnostic test or test modality is
>> recorded in classvar, which must be at least ordinal, with higher values
>> indicating higher risk."
>> 
>> In short -estimates- is irrelevant for running -roccomp-. I suggest that you
>> reread the manual entry for -roccomp-.
>> 
>> Steve
>> 
>> On Jun 28, 2013, at 5:54 PM, Edouard Betsem wrote:
>> 
>> It's still not working.
>> by is not allowed here and using separate returned this error code
>> 
>> [__00000E] not found
>> r(111);
>> 
>> I'm wondering if "roccomp" can be used with "estimates"
>> 
>> I've even renamed the _est_mod1 to mod1. It's on the editor table but I don't know why Stata can't find it
>> 
>>           logistic tma whoall
>>           est store mod1
>>           rename _est_mod1 mod1
>> 
>>           logistic tma study_2
>>           est store mod2
>>           rename _est_mod2 mod2
>>           roccomp tma _est_mod1 _est_mod2, graph summary
>> 
>> the estimates variables return the value "1" for all my observations.
>> Wish someone can help me solve this.
>> Thanks
>> 
>> Edouard BETSEM, MD, PhD
>> 
>> 
>> On 28/06/2013 00:48, Bley N'Dede wrote:
>>> I am not sure but may be you should try something like
>>> 
>>> roccomp _est_mod1 _est_mod2, graph summary by(dis)
>>> ________________________________________
>>> From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] on behalf of Edouard Betsem [edouardbetsem@gmail.coou should try m]
>>> Sent: Friday, June 28, 2013 7:29 AM
>>> To: statalist@hsphsun2.harvard.edu
>>> Subject: st: Can't store estimates
>>> 
>>> Hi,
>>> I'm trying to use roccomp commande to compare AUC for two logistic
>>> models. but stata won't store my estimates.
>>> 
>>> here are the commande lines.
>>> 
>>> * all counts with binary
>>>             logistic dis ref
>>>             est store mod1
>>> 
>>>             logistic dis stud
>>>             est store mod2
>>>             roccomp dis mod1 mod2, graph summary
>>> 
>>> and this is the message i have:
>>> 
>>> variable mod1 not found
>>> r(111);
>>> 
>>> does anyone know the reason for this?
>>> Best
>>> Edouard
>>> 
>>> 
>>> 
>>> 
>>> --
>>> Edouard BETSEM, MD, PhD
>>> 
>>> 
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> 



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