Calculate difference between values on timechart

[dataisbeautiful]

Hi all

I'd like to plot the difference between two values on a timechart

Example data:

_time	a	b
t	10	1
t+1s	11	1.5
t+2s	12	2

Expected resulting data

time	a	b	c
t	10	1	9
t+1s	11	1.5	9.5
t+2s	12	2	10

I'm using the query

index=indx sourcetype=src (Instrument="a" OR Instrument="b")
| eval c = a - b
| timechart values(a) values(b) values(c) span=1s

Any ideas where I'm going wrong?

[gcusello · Accepted solution]

Hi @dataisbeautiful,

try to add eval after the timechart:

index=indx sourcetype=src (Instrument="a" OR Instrument="b")
| timechart values(a) values(b) span=1s
| eval c = a - b

Ciao.

Giuseppe

[dataisbeautiful]

Thank you @gcusello, that worked