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| From | "Nick Cox" <n.j.cox@durham.ac.uk> |
| To | "Statalist" <statalist@hsphsun2.harvard.edu> |
| Subject | st: RE: sort of standardization |
| Date | Wed, 12 May 2010 20:04:39 +0100 |
Several answers to this all I think omitted one point about PCA. Standardisation in the sense of (value - mean) / sd is unnecessary before PCA because you only need ask for a PCA based on a correlation matrix. However, you're not guaranteed the same result with (value - min) / (max - min) OR value / (max - min). Nick n.j.cox@durham.ac.uk From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Ginevra Biino I have to standardize many variables (in order to run PCA). Besides generating the n corresponding std(varname) vars, which I have already done, I also want to generate n new variables obtained dividing each variable by its range. Can anybody help me? * * 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/