[Lens] Shortcut to formula percentage change as an option in differences

[wylieconlon]

This functionality is possible using lens formula, however this issue can increase discoverability.

This calculation is defined as the percentage change of the current value compared to the previous value. It can be positive, negative, or undefined. The rate of change is defined as (current value - previous value) / previous value.

User input

This function doesn't have any required user input.

Form design

No design yet.

Table example with gap skipping (default)

timestamp per 3 hours	Count	Percentage change
2020-08-21 15:00	10	-
2020-08-21 21:00	-	-
2020-08-21 18:00	19	-
2020-08-22 00:00	22	15.79%
2020-08-22 03:00	13	-59.0%

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)

[flash1293]

It's possible to do this via formula as well (it will be documented how this works), this issue is tracking the addition of an option for the differences function so it's not necessary to use formula for this common case.