Figure 4
From: Solar irradiance monitoring network design using the variance quadtree algorithm
L–method benchmarking. Evaluation graphs for determining the optimal number of clusters using the stratum variance, Davies-Bouldin (DB) index, the Caliński-Harabasz (CH) index, and the L-method. (a) shows the mean stratum variance Q h at each iteration. (b) shows the overall root-mean-square error using the L-method for each possible separation. (c) shows the best fit partition of 7 iterations (i.e., 22 stations). (d) shows the best DB index for different number of clusters over a total of 20 repeats of the k-means clustering. (e) and (f) show R M S E DB and the best fit L-method partition given by the DB index, respectively. Twenty-four clusters give the smallest R M S E DB . Subplots (g-i) show the respective plots for the CH index. Twenty-three clusters give the smallest R M S E CH .