 This is not the case in practice as the authors demonstrate by generating the anomaly score map produced for the distribution by the Isolation Forest algorithm.Although the anomaly scores correctly increase as the points move radially outward, they also generate rectangular regions of lower anomaly score in the x and y directions, compared to other points that fall roughly at the same radial distance from the centre.It is possible to demonstrate that these unexpected rectangular regions in the anomaly score map are indeed an artifact introduced by the algorithm and are mainly due to the fact that the decision boundaries of Isolation Forest are limited to be either vertical or horizontal (see Fig.