Hi @Lyons_Zhang,
See this post. This method only operates on categorical data, but you can trick QIIME into interpreting data as categorical by adding non-numeric characters. For example, 1, 2, 3 could become:
I, II, III
one, two, three
1_, 2_, 3_
In a future release of QIIME2, we plan to provide an easier approach to allow QIIME to interpret numeric columns as categorical. We will post to this thread to announce this change when it occurs. Stay tuned!