Visualization of different metrics and the relations between these metrics. Given two classes, red class and blue class. The black circle represents a classifier that classifies the sample inside the circle as red samples (belong to the red class) and the samples outside the circle as blue samples (belong to the blue class). Green regions indicate the correctly classified regions and the red regions indicate the misclassified regions. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).