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From |
Francesca Pesola <PesolaF@cardiff.ac.uk> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Use of polychoricpca with imputed data |

Date |
Thu, 8 Mar 2012 18:04:37 +0000 |

Thanks for your reply. I used the -category(manip)- option and it seems to have worked; what I am not sure about is how well. I am working with survey data and have a number of alcohol items which I need to combine; unfortunately, they are not from a standard questionnaire which is why i set off to use -polychoricpca-. Once I run the PCA, I use the factor scores as a predictor in a number of regressions. When I compare the regression output for the imputed data to that of the complete cases, results are similar. Do you think for the purpose of my analyses, the use of -category(manip)- is appropriate? Could you recommend some articles and/or sites on how to use the -program, eclass- command? Thanks again. -----owner-statalist@hsphsun2.harvard.edu wrote: ----- To: statalist@hsphsun2.harvard.edu From: Stas Kolenikov Sent by: owner-statalist@hsphsun2.harvard.edu Date: 03/08/2012 05:34PM Subject: Re: st: Use of polychoricpca with imputed data It is not going to work out satisfactorily. -polychoric- is not an estimation command, in the sense of producing proper -e(b)- and -e(V)- matrices that -mim- could pick up. A reasonable way to proceed would be to write your own -program, eclass- that would accept [pw] and [if] conditions (that -mim- uses), would run -polychoricpca- on the sample it receives, and use it in a further estimation command such as -regress- (which would still produce underestimated standard errors that won't account for sampling variability in the predicted scores). If you want to get some sort of averaged scores, you can try -category(manip)-, although I am not entirely sure what the interpretation of the results would be. If you would explain the analytic purpose of your exercise, may be I'd come up with better suggestions. I've been meaning to rewrite -polychoric- as a wrapper for -cmp-, so that it would produce appropriate standard errors (which ain't rocket science given how much work David Roodman put into his wonderful package). Whether I will ever do that is an open question. On Thu, Mar 8, 2012 at 5:31 AM, Francesca Pesola <PesolaF@cardiff.ac.uk> wrote: > I have imputed my dataset using the 'mi ice' command in Stata 11 and I would like to run a principal component analysis, using the 'polychoricpca' command, on the imputed data. I am interested in saving the extracted component to the dataset to use it in my analyses. > > I used mim2: polychoricpca varlist, pw score(outcome) nscore(3) > > > But I received the following message: > > command polychoricpca not recognised by mim; try specifying category option > r(198); > > > How can I specify the category option? > Cheers, > Francesca > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ -- Stas Kolenikov, also found at http://stas.kolenikov.name Small print: I use this email account for mailing lists only. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: Use of polychoricpca with imputed data***From:*Stas Kolenikov <skolenik@gmail.com>

**References**:**Re: st: Use of polychoricpca with imputed data***From:*Stas Kolenikov <skolenik@gmail.com>

**st: Use of polychoricpca with imputed data***From:*Francesca Pesola <PesolaF@cardiff.ac.uk>

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