findAdjacentFeature: Find adjacent features of given feature
In fchen365/surf: Statistical Utility for RBP (RNA binding protein) Functions

Locate the adjacent bins at the desired direction and extract the genomic bins, given some location features of AS events. This is a helper function to getFeature().

findAdjacentFeature(
  plas,
  body,
  type = c("lead", "lag"),
  depth.exon = 100,
  depth.intron = 300
)

`plas`	one isoform element in `isoPLas`.
`body`	`list`, $id_tx, $event_id = body bins indices.
`type`	`character`, either"lead" for upstream, or "lag" for downstream.
`depth.exon`	`integer`, extended depth into exon, default 100 nt.
`depth.intron`	`integer`, extended depth into intron, default 300 nt.