How to show difference between two fields?

from(bucket: “a_bucket”)

|> range(start:-100d)

|> filter(fn: (r) =>

  r._measurement == "closes" and

  (r._field == "A" or r._field == "B")


|> yield()

above would show values of “A” and “B” and now I want to show the difference between “A” and “B”; how?

Maybe just use a Binary operation Transform like this?

thanks a lot; this is exactly what I want to;
in addition, shall I modify “backend_02” and “backend_01” by adding variables; for examples, I define two “Text box”/“Custom” variables: “text_box_1” and “text_box_2” like below:

I want to edit them directly;

Glad the binary transformation will do the trick.

No idea if adding variables will work, so give it a try and post the results here.