PCA and cluster analysis of the recorded cells based on both physiological and morphological properties. (A) Scree plot of the eigenvalues derived from PCA of the 30 variables (12 functional and 18 structural). The first seven factors together accounted for 78.5% of the total variance. (B) Joining tree of agglomerative clustering using the first seven principal component factor scores for each cell (37 cells in total for which all 30 parameters were determined). The individual cells are shown on the x-axis and the normalized maximum Euclidean distances between any two cells are shown on the y-axis. At the bottom, the group membership of each cell is shown based on clustering of either only the physiological or only the morphological parameters. Note the almost perfect matching between the three ways of clustering. (C) Cumulative probability plot of squared Euclidean distances of cells in clusters 1 (solid) and 2 (shaded) from the centre of cluster 1. (D) Cumulative probability plot of squared Euclidean distances of cells in clusters 1 (solid) and 2 (shaded) from the centre of cluster 2. The distributions in both panels C and D are significantly different from each other (Mann–Whitney, P < 0.001). σ2, variance; Dlink, linkage distance; Dmax, maximum linkage distance.