extracts the matrix of detrimental information with one of these methods: IIR ('iirp'), EPO ('epo'), EROS('eros' ou 'epoe')
dmatrix = pop_dextract(method,x_ed,(classes_indiv),(classes_perturb))
a matrix (n1 x q) from an experimental design or a Div structure
a vector identifying the individuals of x_ed (for 'epo','eros' or 'epoe')
a vector identifiant the level of detrimental influence for each observation of xg ( for 'epo')
a matrix containing only detrimental information
the dimensions of dmatrix.d depend on the chosen method