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. Author manuscript; available in PMC: 2016 Feb 1.
Published in final edited form as: Respir Physiol Neurobiol. 2014 Dec 12;207:28–39. doi: 10.1016/j.resp.2014.11.016

Figure 6.

Figure 6

Statistical Method to determine the optimal number of clusters of the data set. Upper panel: Plot of the normalized sum of squared distance (SSk) vs. the number of clusters (k) decreases as a function of k. Lower Panel: Plot of a function of the ratio of SSk to SSk-1 enhances the detection of the relative decrease in total variance of the data set that the addition of cluster k contributes. See text for details.