Thank you for the explanation Dr Philipp.
On Thursday, May 25, 2017 at 10:16:06 PM UTC+8, mitt...@univie.ac.at wrote: > > As an exploratory technique, PCA makes no distributional assumptions; it > is used to explore the empirical distribution of the data. The sample does > not need to be balanced with regard to sex or other grouping variables, but > larger groups have a stronger effect on the PCA than smaller groups. > > The origin of the coordinate system is arbitrary. However, many software > packages center the data so that the origin (i.e. where the axes intersect) > equals the mean value. > > > > Am Donnerstag, 25. Mai 2017 09:58:31 UTC+2 schrieb Helmi Hadi: >> >> Dear morphometricians, >> >> Does a sample need to be normally distributed when conducting PCA in >> geometric morphometrics? Sometimes due to research constraints there are no >> samples of the opposite sex. Someone was asking me this question, and I do >> not have the answer. When I look at the data distribution, there is quite >> an imbalance male/female population. However, the classifiers male/female >> and species are there and you can sort of tell which group belongs to >> where. My only fear is that the confidence ellipse for the males are being >> "gravitated" towards the females for one species as that species does not >> have any male specimens. Attached are the file which I have recreated the >> dataset based on memory. >> >> Is this kind of data acceptable or publishable? >> >> My own personal question is based on the GMM results given in MorphoJ. >> The PC1/PC2 axes does not intersect at the middle (which I have personally >> drawn the dotted line there). I don't mind this output, but does it matter >> to have the axes cut at the 0 value? The data data distribution does not >> change with the change of axes lines. I noticed some GMM papers have the >> axes at 0. >> >> Thanks all for the help, >> >> Helmi Hadi, >> School of Health Scienes, >> Universiti Sains Malaysia >> > -- MORPHMET may be accessed via its webpage at http://www.morphometrics.org --- You received this message because you are subscribed to the Google Groups "MORPHMET" group. To unsubscribe from this group and stop receiving emails from it, send an email to morphmet+unsubscr...@morphometrics.org.