New subject: Running a simple IRT model...

1 Aug 2006

On 7/31/06, Eduardo Leoni &lt;eleoni(a)hmdc.harvard.edu&gt; wrote:
...
  "Y1, Y2, and Y3: Y1 contains the items for
subject ``Y1'', Y2 contains the
 items for subject ``Y2'', and so on"

 are you sure variables are in the columns? 
   I assume so.  Just to be clear, I have about 30 variables and
about 1,200 cases, so I should have cbind(Y1, Y2, Y3, ... , Y1199,
Y1200) in the call, right?

...
  anyway, just using MCMCpack might
 currently a better option.

 library(MCMCpack)
 posterior<-MCMCirt1d(vars)
 summary(posterior) 
  That certainly does seem easier, since cbind(names(m)) gives me an
error, and I really don't want to hand-code all 1200 case ids in the
call to the IRT model.  But it looks like MCMCirt1d requires a matrix,
and further states:

        The matrix of data.  Must be 0, 1, or missing values.   The
         rows of 'datamatrix' correspond to subjects and the columns
        correspond to items.

   That's not what I've got, which is a bunch of variables scaled
from 0 to 1.  Is that a problem, or does this model only work on
binary data?

-- Chris

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Re: [zelig] Running a simple IRT model...