Using biom from QIIME to make venn diagram

I have

  • a biom file with individual samples from QIIME.
  • a mapping file with a column containing groups based on which I want to collapse samples

I want to

  • convert the biom file into .shared file
  • group samples in the shared file according to the description in the column in mapping file
  • make a venn diagram

Issues I ran into

  • the shared file given by make.shared(biom=*.biom) is empty
  • I have no idea how to group multiple samples into one according to mapping file data