Parameter optimization plot for microarray example. Classification error rates for primary fibroblast cell lines between three separate species determined by different epsilon values for (a) the spectral method from Ng et al. and (b) kernel PCA. Epsilon values were increased to 5 × 109 to assess classification accuracy (data not shown), but truncated for the plot to better visualize the global minima for each classifier method. The spectral method from Lafon has a 0% error rate across all methods except LDA, where only one sample is misclassified.