Kibana 6.1.2 - understanding serial diff aggregation

[asp]

Hi,

I upgraded from 5.1.2 to 6.1.2 and I am checking whats new in 6.1.2.
Serial Diff aggregation sounds interesting:

As I understand it is building the difference between current and previous buckets. As I understand it is possible to to configure which bucket to substract by setting the lag field.

1. Is it possible to define which bucket to use within kibana, or is this feature only supported when dealing with ES directly?
2. Is it possible to set a time offset for building the difference like timelions offset function?

[ppisljar (Peter Pisljar)]

here is the docs for serial_diff aggregation:
https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-pipeline-serialdiff-aggregation.html

you can specify the lag with advanced json input, something like:

{
"lag": 7
}

you can't just offset your series with this, it will always calculate the difference to previous buckets