Ekman data set
Object of class
Ekman presents similarities for 14 colors which are based on a rating by 31 subjects where each pair of colors was rated on a 5-point scale (0 = no similarity up to 4 = identical). After averaging, the similarities were divided by 4 such that they are within the unit interval. Similarities of colors with wavelengths from 434 to 674 nm.
Ekman, G. (1954). Dimensions of color vision. Journal of Psychology, 38, 467-474.