Fig. 10
From: Facial expression recognition and histograms of oriented gradients: a comprehensive study
![Fig. 10](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40064-015-1427-3/MediaObjects/40064_2015_1427_Fig10_HTML.gif)
HOG optimization results (RFD with 7 expressions): the x-axis reports the cell size in pixel and the y-axis refers to the average recall percentage