Diagnostic diagram showing log([O iii]λλ5007,4959/Hβ) versus log([N ii]λ6584/[O ii]λ3727) for models computed with SAL2 IMF. Each panel shows a different metallicity model and the corresponding data in that metallicity range. Symbols have the same meaning as in Fig. 9, with the addition of the blue dots, which correspond to H ii regions from Yin et al. (2007).