Fig. 7
From: Euler diagrams drawn with ellipses area-proportionally (Edeap)
Missing two-or-more-label region criterion. a Case 1 draws the ellipse \(e_b\) towards the region “a c” by penalising the distance between the centre of \(e_b\) and a known point in region “a c”. b Case 2 aims to push the ellipse \(e_b\) away from both ellipses \(e_a\) and \(e_c\) to create the missing region “a c”. Once region “a c” exists the region area difference criterion will work to adjust to the appropriate region proportions, but can’t do this until the region “a c” is created (outside of “a b c”)