I run R to calculate ability values of about 20k students who took a test. I
face the following issues.


   - I am unable to get output with entries for all the students. Getting
   output using write.table option works but I found about 100 entries missing.
   - How to get output of item parameters upon fitting 3PL model in an
   external text file?


   - Is it possible to feed in response matrix along with unique student ids
   and get the output along with student ids? If yes, how?
   - At times a get a warning message "Hessian matrix is convergence is not
   positive definitite; solution is unstable." What could be the reason for
   this?
   - Can I run R script from PHP?

Regards,
Maulik Shah

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