reFABS = function(V, C, R=5, Q=1000):
V: Set of binding sites
C: Mapping criterion
R: No. of sampling runs for step A
Q: No. of sampling runs for step B

1. Estimate number of sites to be sampled randomly
1. Map V using C and note down the number of genes (N) mapped
2. Treat all binding sites mapped to a gene as duplicates and let M be the number of such non-duplicate binding sites.
3. Sample M sites randomly
4. Map the M random sites using C and note down number of genes mapped
5. Repeat steps 2 to 4 for R times
6. N’ is the average number of genes mapped in the steps 2-4 over R runs
7. M’, the number of random sites to be sampled, = M×N/N’

1. Estimate Significance of Enrichment
2. Map V to genes using C. Let nz be the number of genes mapped to the predefined gene category Z
3. Randomly sample M’ sites from the reference genome
4. Apply the criterion C, map M’ binding sites to genes
5. Let n_iz’ be the number of mapped genes using M’ in Z in i_th sampling run.
6. Repeat steps 2-4 for Q times
7. p-value of the category Z, P_z, is the fraction of Q sampling trials yielded niz’ ≥ n_zi.e. P_z= |{i | i = 1…Q and  n_iz’ ≥ nz}|/Q