Scatter plot of the melanoma sample dataset of Haqq et al.

This is the same set of samples of Figure 4 and we have used the same color coding. We are now using the modified statistical complexity measures M-skin and M-metastasis II. As expected, normal skin samples (in green) have a low value of the M-skin measure. Interestingly, most of the nevi samples (in yellow) have an intermediate value of the M-skin measure, and most of the primary and metastatic samples have even larger values of M-skin. This result, together with our observation and analysis of Figure 4, indicate that the Jensen-Shannon divergence of melanoma samples from the normal skin profile may be a relevant measure to quantitatively analyse progression even when the whole gene expression dataset is used. We observe that, although the M-metastasis II measure has used all the samples labelled as Type 2 (in Haqq et al.'s original contribution), their position in this plane shows two different clusters. This may indicate that a further heterogeneity may exist in this subgroup, a fact that warrants further study with a larger group of samples.