title: R overlap multiple GRanges with findOverlaps()
body: <p>I have three tables with differing genomic intervals. Here is an example:</p>
  
  <pre><code>&gt; a
     chr interval.start interval.end names
  1 chr1              5           10     a
  2 chr1              6           10     b
  3 chr2              7           10     c
  4 chr3              8           10     d
  
  &gt; b
     chr interval.start interval.end names
  1 chr1              6           15     e
  2 chr1              7           15     f
  3 chr1              8           15     g
  
  &gt; c
     chr interval.start interval.end names
  1 chr1              7           12     h
  2 chr1              8           12     i
  3 chr5              9           12     j
  4 chr10             10          12     k
  5 chr20             11          12     l
  </code></pre>
  
  <p>I am trying to find the common intervals between all tables after converting info to GRanges.  Essentially I want to do something like intersect(c,intersect(a,b)).  However, because I am using genomic coordinates, I have to do this with GRanges and GenomicRanges package, which I am not familiar with.</p>
  
  <p>I can do findOverlaps(gr, gr1) or findOverlaps(gr1, gr2), but is there an easy way to overlap multiple GRanges at once like findOverlaps(gr, gr1, gr2)?</p>
  
  <p>Any help would be appreciated.  If this question was asked elsewhere, I apologize in advance.</p>
  
  <p>Thanks</p>