[R] Problem detect cheating with CopyDetect Package

Jeff Newmiller jdnewmil at dcn.davis.ca.us
Thu Aug 18 08:07:22 CEST 2016

If we R users unfamiliar with the details of the CopyDetect package are to be able to help,  we would need a reproducible example that includes data. See to http://www.catb.org/esr/faqs/smart-questions.html and http://adv-r.had.co.nz/Reproducibility.html for discussion on how to ask for help online.

I will make a wild guess that your data is nowhere near as broadly variable as this algorithm needs in order to work... but it might just be incorrect specification of parameters. Either way you have hidden the answers from us. If you think the package is broken or you need help with the theory you should identify the maintainer with the maintainer() function and correspond with them. 

Sent from my phone. Please excuse my brevity.

On August 16, 2016 7:13:41 PM PDT, Ahmad Nursalim <ceritaahmad at gmail.com> wrote:
>Dear All list members,
>Please Help me
>I have the problem detect cheating analysis with use of CopyDetect
>I use my own data
>namely data.abcd and slopintrc
>and when I tried to count by R studio with a script
>for (i in 1: replication) {
>   x <- CopyDetect2 (data = data.abcd,
>                    item.par = slopintrc,
>                    pair = c (pairs [i, 1], pairs [i, 2]),
>                    options = c ("A", "B", "C", "D", "E"))
>   pairs [i,] $ W = x $ W.index $ p.value
>   pairs [i,] $ GBT = x $ GBT.index $ p.value
>   pairs [i,] $ K = x $ K.index $ k.index
>   pairs [i,] $ K1 = x $ K.variants $ K1.index
>   pairs [i,] $ K2 = x $ K.variants $ K2.index
>   pairs [i,] $ S1 = x $ K.variants $ S1.index
>   pairs [i,] $ S2 = x $ K.variants $ S2.index
>an error
>Error in solve.default(object$hessian) :
>  system is computationally singular: reciprocal condition number =
>2.52915e-29In addition: Warning message:In ltm.fit(X, betas,
>constraint, formula, con) :
>Hessian matrix at convergence is not positive definite; unstable
>Please help me
>	[[alternative HTML version deleted]]
>R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>PLEASE do read the posting guide
>and provide commented, minimal, self-contained, reproducible code.

More information about the R-help mailing list