Correlation analysis for the 24 hours leading up to the flare SOL2011-02-13T17:28M6.6. The normalized event epochs of the unsigned helicity of the current-carrying field (|H_J|) and the free magnetic energy (E_F) are shown in the vertically and horizontally oriented line profile, respectively. The accumulated cost matrix is shown color-coded. The white dotted line represents the optimal (warping) path.