title: Venn Diagram from GRanges
body: <p>I have granges objects like these( showing two of the four):</p>
  
  <pre><code>&gt; upmd_Hf3a
    GRanges object with 398117 ranges and 2 metadata columns:
         seqnames                 ranges strand |        type       nCG
            &lt;Rle&gt;              &lt;IRanges&gt;  &lt;Rle&gt; | &lt;character&gt; &lt;integer&gt;
     [1]     chr1       [     1, 714170]      * |         PMD       280
     [2]     chr1       [714171, 732041]      * |      notPMD       103
     [3]     chr1       [732042, 762741]      * |         PMD       109
     [4]     chr1       [762742, 796127]      * |      notPMD       264
     [5]     chr1       [796128, 859047]      * |         PMD       829
     ...      ...                    ...    ... .         ...       ...
  [398113]     chr9 [140133051, 140174235]      * |      notPMD      1725
  [398114]     chr9 [140174236, 140176229]      * |         PMD       187
  [398115]     chr9 [140176230, 140187041]      * |      notPMD       219
  [398116]     chr9 [140967724, 140973103]      * |      notPMD       152
  [398117]     chr9 [140973104, 141042747]      * |         PMD      1145
   seqinfo: 93 sequences from an unspecified genome
  
  &gt; upmd_Hf3b
  GRanges object with 334247 ranges and 2 metadata columns:
         seqnames                 ranges strand |        type       nCG
            &lt;Rle&gt;              &lt;IRanges&gt;  &lt;Rle&gt; | &lt;character&gt; &lt;integer&gt;
     [1]     chr1       [     1, 712661]      * |         PMD       274
     [2]     chr1       [712662, 734889]      * |      notPMD       116
     [3]     chr1       [734890, 770103]      * |         PMD       152
     [4]     chr1       [770104, 794246]      * |      notPMD       163
     [5]     chr1       [794247, 859587]      * |         PMD       855
     ...      ...                    ...    ... .         ...       ...
  [334243]     chr9 [137315552, 137325053]      * |      notPMD       265
  [334244]     chr9 [138776843, 138782261]      * |         PMD       119
  [334245]     chr9 [138782262, 138854249]      * |      notPMD      1899
  [334246]     chr9 [139633630, 139648757]      * |         PMD       391
  [334247]     chr9 [140835156, 140917488]      * |         PMD      1169
  -------
  seqinfo: 93 sequences from an unspecified genome
  </code></pre>
  
  <p>I have used MethylSeekR to create (predict paritally methylated domains-PMDs) these GRanges objects. I want to plot venn diagram for the PMD (for the column "type") regions for all these GRanges objects to show the overlap. Can anyone please help me with this ? Thanks a lot in advance</p>