/ (F+R). D ranges between −1 and 1 and specifies the bias in expression to reverse and forward strand, respectively (D=0 means 50% reverse and 50% forward strand expression, while abs(D) close to 1 indicates unidirectional transcription). A directionality score calculated from pooled data is a good estimate of sample directionality (Supplementary Fig. 6b). Each bidirectional locus was assigned one expression value for each sample by summing the normalized expression of the two flanking windows.
