Preflare values of selected measures. (a) Flux-normalized helicity of the current-carrying field vs. free energy ratio, and (b) helicity ratio vs. free energy ratio, for the event sample S​_major. (c) Critical height for torus instability vs. helicity ratio and (d) normalized flare distance vs. helicity for the event sample S​_CBetal. Numbers in brackets indicate the ratio of confined to eruptive flares within the tested sample. Blue and red color indicates confined and eruptive flare type, respectively. X-class and M-class flares are shown as stars and circles, respectively.