R help - Dec 2008 - Calculating Sensitivity, Specificity, and Agreement from Logistics Regression Model

Hi,

Assume I have a variable Y having two discrete values and two predictor
variables x1 and x2.
I then do a logistic regression model fit as:

fit<-glm(Y~x1+x2,family=binomial). Are there functions in R than calculate
the
Sensitivity, Specificity , and Agreement of the model "fit"?

Thanks
Meir





********************************************
Meir Preiszler - Research Engineer
I t a m a r M e d i c a l Ltd. 
Caesarea, Israel:
Tel: +(972) 4 617 7000 ext 232
Fax: +(972) 4 627 5598
Cell: +(972) 54 699 9630
Email: pmeir@itamar-medical.com 
Web: www.Itamar-medical.com 
*********************************************




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Meir Preiszler wrote:
> Hi,
> 
> Assume I have a variable Y having two discrete values and two predictor
variables x1 and x2.
> I then do a logistic regression model fit as:
> 
> fit<-glm(Y~x1+x2,family=binomial). Are there functions in R than
calculate the
> Sensitivity, Specificity , and Agreement of the model "fit"?
> 
> Thanks
> Meir
Beware as those 3 measures are discontinuous functions of x1 and x2, 
requiring completely arbitrary dichtomizations, and are improper scoring 
rules in the statistical sense.

Frank
> 
> 
> 
> 
> 
> ********************************************
> Meir Preiszler - Research Engineer
> I t a m a r M e d i c a l Ltd. 
> Caesarea, Israel:
> Tel: +(972) 4 617 7000 ext 232
> Fax: +(972) 4 627 5598
> Cell: +(972) 54 699 9630
> Email: pmeir at itamar-medical.com 
> Web: www.Itamar-medical.com 
> *********************************************
> 
> 
> 
> 
>
----------------8<--------------------8<-------------------8<-------------------
>  This E-mail is confidential information of Itamar medical Ltd. It may also
>   be legally privileged. If you are not the addressee you may not copy,
forward,
>   disclose or use any part of it. If you have received this message in
error,
>   please delete it and all copies from your system and notify the sender
>   immediately by return E-mail. Internet communications cannot be
guaranteed
>   to be timely, secure, error or virus-free. The sender does not accept 
>   liability for any errors or omissions. Before printing this email , 
>   kindly think about the environment.       Itamar Medical Ltd. MIS Yan
Malgin.
>
----------------8<--------------------8<-------------------8<-------------------
> 
> 
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> 
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 

-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University

> Von: Frank E Harrell Jr <f.harrell@vanderbilt.edu>
> Datum: 18. Dezember 2008 14:49:53 MEZ
> An: Meir Preiszler <pmeir@Itamar-Medical.com>
> Kopie: r-help@r-project.org
> Betreff: Re: [R] Calculating Sensitivity, Specificity, and Agreement  
> from Logistics Regression Model
>
>
> Meir Preiszler wrote:
>> Hi,
>> Assume I have a variable Y having two discrete values and two  
>> predictor variables x1 and x2.
>> I then do a logistic regression model fit as:
>> fit<-glm(Y~x1+x2,family=binomial). Are there functions in R than  
>> calculate the
>> Sensitivity, Specificity , and Agreement of the model "fit"?
>> Thanks
>> Meir
>
> Beware as those 3 measures are discontinuous functions of x1 and x2,  
> requiring completely arbitrary dichtomizations, and are improper  
> scoring rules in the statistical sense.
Hi Frank, maybe you should take a look at the ROCR package. I use it a  
lot (as well with logistic regression), it can plot and calculate many  
classification relevant indices.

Felix
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