PCA analysis for EV Lac. (a) Mean profile (red) for all observations and its decomposition in the antisymmetric (blue dashed) and symmetric (yellow dotted) component (with respect to the line centre) related to the poloidal and toroidal axisymmetric field, respectively. (b) First three eigenvectors of the mean-subtracted Stokes V profiles. (c) Mean profile (left column), and the coefficients of the first three eigenvectors (three columns to the right) for each season (one season per row). The mean profiles of the individual seasons are plotted in the same format as in panel a. The coefficients are colour-coded by rotation cycle.