Trustworthiness of the visualized similarities (neighborhoods of k nearest samples). Sammon: Sammon's mapping, NMDS: non-metric multidimensional scaling, SOM: self-organizing map, HC: hierarchical clustering, with the ultrametric distance measure and with the linear distance measure. RP: Random linear projection is the approximate worst possible practical result (the small standard deviation over different projections, approximately 0.01, is not shown). The theoretical worst case, estimated with random neighborhoods, is approximately M1 = 0.5. a) Yeast data. b) Mouse data.