Subtract between 2 fields

Hi guys.
im trying to subtract filed A from filed B
example i have a Casino system and i want to make a substuct to get the profit
so i want WinAmount-BetPlaced so it will give me a profit value.
can it be done?

Grafana does not support any operations on time series this should be done by the database.

We have been discussing supporting operations on timeseries but its currently not on our roadmap

ok thanks
eventually i made a grok + ruby under my logstash
so im making the calculation there and my Grafana show this filed