Scaled principal components for samples in the time-course experiment, with the axes found in different sets of data. Data were obtained for mammary gland development (Anderson et al., 2007); groups 0 to 5: days 1 to 19 of pregnancy; groups 6 to 8: days 1 to 9 of lactation, group 9: day 2 of involution . A. Results of the original method. The axes were found with all samples of 12,487 genes. Scaled principal components (sPC) of the first and second axes are shown. B. Axes were found in 5,892 positive genes with the analysis of variance test. C. Axes were found in the training data, prepared by using each group's sample means of 12,487 genes. D. An example of biplot-like presentation. Scaled principal components for the training data for gene items (open circles) and groups (0 to 9) are presented in a same scale.