explicit log for picrust otu conversion

Hi All,

I’m using the picrust option in make.biom with great pleasure and no problems.

However, I’d like to track which of the original 97% clustered OTUs were converted to picrust-compatible Greengenes phylotypes. The output could be a two column matrix, where one column is the original OTUs, labeled Otu000001 … Otu038245, and the second column would contain a corresponding Greengenes ID. No Greengenes ID would mean the original OTU was not picrust-compatible. Seems straightforward. How can I make this dream a reality?

EDIT: is it just simply matching taxonomic classifications, perhaps to some level?