vignettes/Vig_08_Notes.Rmd
Vig_08_Notes.RmdThis vignette is based upon LearnPCA version 0.3.4.
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This vignette collects bits of information and answers to questions we have received from our readers, as well as some tips and warnings that may be useful.
Shinn reports that PCA on data which may be shifted in space or time can give “phantom oscillations” that don’t exist in the data. His context is neuroscience but one should be careful with this type of data.
A reader asked if one should center ordinal survey responses, for instance responses on a 1-5 scale. We didn’t know the answer, but after some discussion and research we found there is an R package Gifi designed for just this case. There’s also a tutorial here. Both of these resources use concepts published in a book by Gifi (1990).
In addition to references and links in this document, please see the Works Consulted section of the Start Here vignette for general background.
Professor of Chemistry & Biochemistry, DePauw University, Greencastle IN USA., harvey@depauw.edu↩︎
Professor Emeritus of Chemistry & Biochemistry, DePauw University, Greencastle IN USA., hanson@depauw.edu↩︎