Figure 2

Correlations between variables. (a) Spearman rank correlation coefficients for all pair-wise comparisons between the six variables. All the correlations were significant (p < 0.001) except those marked as 'ns'. NA, not applicable. (b) Correlations between variables of the same type. Correlations were analyzed by ranking the six variables for all the genes, dividing them into quintiles (1 to 5 from higher to lower values; Additional data file 7) and comparing the positions of the two analyzed variables for each gene. Correlations for genes whose variables were included in the same quintile were considered as 'very high'; if they differed in one unit, they were considered 'high', and so on. A difference of four units was considered a 'very low' correlation. The ordinate indicates the proportion of genes in each correlation category. The expected values (grey) were obtained from a random distribution of all possible quintile combinations.