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| From | David Svendsgaard <Svendsgaard.David@epamail.epa.gov> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: PCA with Missing Values (or other factor analysis) |
| Date | Tue, 5 Jul 2011 08:30:53 -0400 |
What about changing the missing values to zero after you do the pca. I would use pca based on the covariance matrix. To change the missing values to zero, use mvencode variablename ,mv(0) where variablename is the name of the variable having missing values. I am assuming you have no missing values other than due to the periods when the person was not in office. David J Svendsgaard, PhD Biostatistician EPA/ORD/NCEA/RTP, Mail Drop B-243-01 Research Triangle Park, NC 27711 Phone (919) 541-4186 Fax (919) 541-1818 From: Nick Eubank <nickeubank@gmail.com> To: statalist@hsphsun2.harvard.edu Date: 07/03/2011 12:17 AM Subject: st: PCA with Missing Values (or other factor analysis) Sent by: owner-statalist@hsphsun2.harvard.edu Hello All, I'm trying to do a PCA on legislator votes (1 or 0), where different legislators have overlapping but distinct terms. In other words, legislator A is in office periods 1 and 2, legislator B is in office 2 and 3, so A has no votes in period 3 and B has no votes in period A. I want to map their "ideal points" (i.e. pca predicted value from votes) into the same space. But PCA obviously dislikes missing values. Suggestion? I'm really open to any factor analysis algorithm. Thanks! Nick -- PhD Student, Political Economics Stanford University GSB nickeubank@gmail.com Cell: +1 (303) 918.6528 * * 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/