To better assess the bimodality of the null distributions, for each link we drew 1000 GC and log(ATACseq peak sum of counts + 1) matched trans-peaks using Signac’s function MatchRegionStats() (instead of the default 200), computed their Pearson R and scaled them. To establish if the resulting null distributions were multimodal, we used the mixtools package expectation–maximization function normalmixEM() with k = 2 and epsilon = 1e−03 as described in Ameijeiras-Alonso et al., 201922 (link). Null distributions with nominal p-values < 0.05 were categorised as multimodal.
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