I encountered a minor issue with the handling of metadata.tsv file in qiime2-2018.2.
I had a problem when using only numeric values in the first column (#SampleID) of the metadata.tsv (the problem did not occur in release 2017.12).
I imported and demultiplexed fastq files according to the Moving Pictures Tutorial. After demultiplexing, I applied
qiime quality-filter q-score and used
qiime metadata tabulate to visualize the outcome of filtering (also according to the moving pictures tutorial)
qiime metadata tabulate, I encountered the following error:
There was an issue with viewing the artifact demux_filtered_stats.qza as QIIME 2 Metadata:
Detected non-string metadata ID: 101
(101 is the name of my first sample)
When testing the metadata.tsv file with Keemei, no problem was indicated.
I solved this problem by adding letters to the numeric values of the #SampleID column (changing 101 to sample101). It did not matter, If I used the optional comment directive
#q2:types in the #SampleID column or not (as described in the Metadata Tutorial).
Maybe this helps, if people encounter the same problem.