Fig. 3
Clustering of subjects based on DNA methylation at CpG sites in OPRM1, TLR4, and LINE1, obtained using unsupervised machine learning. U-matrix visualization of the data structure found via a projection onto a toroid neuronal grid using a parameter-free polar swarm, Pswarm consisting of so-called DataBots, which are self-organizing artificial “life forms” that carry vectors of the DNA methylation. a The U-matrix visualization was colored as a top view of a topographic map with brown (up to snow-covered) heights and green valleys with blue lakes. Watersheds indicate borderlines between two different clusters. b Superimposing the pain phenotype group structure indicated considerable coincidence with the cluster separation, which was supported by a significant χ2 test of the cross table of clusters versus pain phenotype groups. Please note the different meaning of the coloring of the data points in the two panels, cluster in panel a but pain phenotype groups in panel b. The figure has been created using the R software package (version 3.4.4 for Linux; http://CRAN.R-project.org/ [40]) and the library “DatabionicSwarm”, https://cran.r-project.org/package=DatabionicSwarm [64])