[R] Elliptic Fourier Analysis and PCA

Violette Bertrand violette.bertrand at yahoo.fr
Thu Apr 10 16:05:09 CEST 2014


I use packages "momocs" and "ade4" to dertermine morphometry of 
cavities entrances. 
I have few questions about the PCA 
(non-normalized) (see image enclosed) :

  1) *What do show the confidence 
ellipses ?*  Some papers say that ellipses
include 95 % of the data, but it 
seems to be less here... Moreover, I can choose the size of the ellipses with "cellipse" (ex : cellipse=1), but what does it means ?

  2) What does mean "d=50" (in the top-right corner) ?

  3) What 
do mean each axis of the PCA ? Wikipedia say "Each axis on a PCA
plot is an 
eigenvector of the covariance matrix of shape variables." But
it's not really 
clear for me... What is the axis units ?

Thanks for your help :-)


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