[R] multilevel factor model in lmer

[Dan Powers]

Harold and Dimitris --
Thanks very much. 
Cheers,
Dan


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Daniel A. Powers, Ph.D.
Department of Sociology
University of Texas at Austin
1 University Station A1700
Austin, TX  78712-0118
phone: 512-232-6335
fax:   512-471-1748
dpowers at mail.la.utexas.edu

-----Original Message-----
From: Dimitris Rizopoulos [mailto:dimitris.rizopoulos at med.kuleuven.be] 
Sent: Monday, October 02, 2006 6:05 AM
To: Doran, Harold; dpowers at mail.la.utexas.edu; R-Help
Cc: dmbates at gmail.com
Subject: Re: [R] multilevel factor model in lmer

If you just want to fit the 2PL, without any covariates, then this can 
be currently handled by function ltm() in package ltm.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Doran, Harold" <HDoran at air.org>
To: <dpowers at mail.la.utexas.edu>; "R-Help" <r-help at stat.math.ethz.ch>
Cc: <dmbates at gmail.com>
Sent: Monday, October 02, 2006 12:22 PM
Subject: Re: [R] multilevel factor model in lmer


> Dan:
>
> lmer cannot currently be used for the 2PL. As you note, it is 
> straightforward to estimate the 1PL, but the a-parameters present a 
> current challenge. Doug mentioned to me the other day he is doing 
> some work on this, so I have copied him on this reply.
>
> Harold
>
>
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch on behalf of Dan Powers
> Sent: Sun 10/1/2006 10:15 PM
> To: 'R-Help'
> Subject: [R] multilevel factor model in lmer
>
>
> Hello --
>
> I am curious if lmer can be used to fit a multilevel factor model 
> such as a
> two-parameter item response model. The one parameter model is
> straightforward.  A two-factor model requires a set of factor 
> loadings
> multiplying a single random effect. For example, a logit model for 
> the ith
> subject responding correctly to the jth item (j=1,..,J) is
>
> logit[p(ij)] = a1*item1(i) + ... +  aJ * itemJ(i) +
> lambda1*item1(i)*u(i) + ... + lambdaJ*itemJ(i)*u(i)
>
> where the lambdas are factor loadings, with lambda1 fixed to 1.0 and
> item1-itemJ are dummy variables for the items.
>
> Thanks,
> Dan
>
> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> Daniel A. Powers, Ph.D.
> Department of Sociology
> University of Texas at Austin
> 1 University Station A1700
> Austin, TX  78712-0118
> phone: 512-232-6335
> fax:   512-471-1748
> dpowers at mail.la.utexas.edu
>
> ______________________________________________
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>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 


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