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logistic regression and 3PL model

6 messages · Michael Lau, Jean Coursol, Brian Ripley +2 more

Original
Jean Coursol
# 
The same is true in french under linux. Something changed
from 1.9.1 to 2.0.0.

First, it is necessary to have .inputrc (in $HOME) 
(or $INPUTRC defined) to enter and display 8-bits 
characters under bash and R.

#.inputrc (for readline library)
set input-meta on
set output-meta on
set convert-meta off

Then

Under R2.0.1, I have:
Error: syntax error
[1] "\351"                 # different from R1.9.1 (="??")
[1] "fr_FR"
[1] "??"                    # OK for display

Another solution:

export LC_ALL='fr_FR'      # before loading R

and then Sys.setlocale becomes useless.

Jean Coursol
Brian Ripley
#
On Thu, 25 Nov 2004, Jean Coursol wrote:

            

      
      
      
    

        
No, it is not the same.  Windows XP does this even in the Danish locale, 
and that is a problem (in Windows).

Your problem is simply that you should be using a French locale to use 
French characters.  You should not expect French characters to be 
recognised in a non-French locale, and if they were, that was a bug in R 
1.9.1.

  
  


  


      

    

    

      
      

        


  

        

      John Fox
    

    

      
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Dear Mike,

Pinheiro and Bates discuss a three-parameter logistic growth model in their
Mixed Effects Models in S and S-PLUS, but as far as I know there's no direct
way to fit the 3PL IRT model in R. It should be possible to fit such a model
using one of the general optimisers in R, such as nlm() or optimise(), and I
think that it would be a nice project to produce an IRT package for R. 

Regards,
 John

--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox 
--------------------------------

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Brian Ripley
    

    

      
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On Thu, 25 Nov 2004, John Fox wrote:

        

            

      
      
      
    

        
optim(), not optimize() as there are at least two free parameters, I 
believe.

            

      
      
      
    

        
As I understand it this is a logistic regression and not a logistic growth 
curve, the latter being fitted by least squares.

For a known baseline (which is thus a 2-free PL model but what seems asked 
for here), a glm family can be constructed to allow glm() to do the 
fitting.  This is model described at

http://work.psych.uiuc.edu/irt/modeling_dich1.asp

with c known to be 0.25.  It would certainly be worth having an 
implementation of that in R, with c=0.5 being the most common case.

It is quite straightforward to fit such models by direct optimization of 
the likelihood, and MASS4 p. 445 gives you a template for logistic 
regression that could easily be modified.

            

      
      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Dimitris Rizopoulos
    

    

      
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I don't know if I am missing something, but isn't there also a latent 
variable (trait) that must be integrated out using maybe Gauss-Hermite 
which might complicate a bit the calculations? So is this possible 
with `glm()'?

Best,
Dimitris

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

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


----- Original Message ----- 
From: "Prof Brian Ripley" <ripley at stats.ox.ac.uk>
To: "John Fox" <jfox at mcmaster.ca>
Cc: <r-help at stat.math.ethz.ch>
Sent: Thursday, November 25, 2004 5:13 PM
Subject: RE: [R] logistic regression and 3PL model