Robust stem loops and pre-miRNA predictions. The upper panel shows a plot of the number of robust stem loops versus the size of the genomic sequence they originate from. The data come from the application of our method to viruses  and, for the three at the extreme right-hand side, from the present study (see Subsection "Identification of novel clustered miRNAs"). The linear dependence is very clear and corresponds to an average of 1.2 robust stem loop every kb. The lower panel shows the relation between the number of predicted pre-miRNAs (stem loops with positive SVM score) and the expected number of pre-miRNAs, given by Equation 4. The linear dependence is also clear here, but the slope is smaller than 1, which would have corresponded to a strict equality between the two sets.