Create custom facet names by using an if function

 I covered custom faceting using booleans in this post. The other nice feature with custom facets is that if you don't want the labels "true" and "false" for your facet, you can just drop your boolean into an if function, and you can name your own facets.

In the custom facet I created using booleans, I used this piece of GREL to facet out any 856 |3 data that started with a volume label and didn't have a semi-colon:

and(value.startsWith("v"), not(value.contains(";")))