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