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prcomp & eigenvectors ... ??
2 messages · Natalie Stephenson, Peter Dalgaard
1 day later
On May 28, 2011, at 20:08 , Natalie Stephenson wrote:
Hi ... Please could you help with probably a very simple problem I have. I'm completely new to R and am trying to follow a tutorial using R for Force Distribution Analysis that I got from ... http://projects.eml.org/mbm/website/fda_gromacs.htm. Basically, the MDS I preform outputs a force matrix (.fm) from the force simulation I perform. Then, this matrix is read into R and prcomp is performed. Basically, the tutorial says 'Having run PCA, now is a good time to check the eigenvalue structure.' although it doesn't mention how I actually go about doing that with R. Could anyone tell me how I would be able to check the eigenvalues/eigenvectors?? Thanks so much for your help and I'm sorry if this is a stupid question!!
Not particularly, given that you may be missing some basic theory of PCA. Basically, the loadings of a PCA _are_ the eigenvectors, so e.g. plotting the loadings matrix against the variable number or whatever structure you have on them -- if they are spatial ore temporal measurements, plot against space/time. Something like matplot(loadings(pca), type="l") matplot(times, loadings(pca), type="l") could prove useful (the latter case if your data are really short time series).
Peter Dalgaard Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com