principal component analysis
model=pcana(x,(centering))
a matrix (n x q) or a Div structure
0=not to be centered (by default); 1=to be centered
model.scores.d: scores of the observations onto the eigenvectors
model.eigenvec.d: eigenvectors = loadings
model.var_scores.d: scores of the variables onto the eigenvectors
model.eigenval.d: eigenvalues
model.ev_pcent.d: eigenvalues, percentage
model.x_mean.d: mean of the column vectors of x, of dimensions (q x 1)
model.x_stdev.d: standard deviation of the column vectors of x, of dimensions (q x 1)
model.centered: applied centering option; 1 = centred, 0 = not centred
model.std: standardisation option = 0