Each curve reflects the average adjusted Rand index Ra of clustering quality as the number of clusters is varied. Each data point on a curve is an average over 100 trials of generating and clustering data. Four clustering variations are considered for each data set: the CORE error model, a uniform error model, a Euclidean distance between pairs of expression profiles, and the error-weighted similarity measure between pairs of expression profiles. (A) The figure depicts the results for normally distributed synthetic data generated from 50 classes. (B) The figure depicts the results from periodic time series synthetic data generated from 4 classes. (C) The figure shows the results of clustering 904 E. coli genes belonging to 275 multi-gene operons based on expression data from 55 experiments. (D) Based on expression data from 20 experimental conditions, the figure shows the results of clustering 205 yeast genes which have each been annotated with one of four functional classifications.