Remove example and experimental

Signed-off-by: Levi Harrison <git@leviharrison.dev>
pull/9248/head
Levi Harrison 3 years ago
parent a16a4cad2d
commit a7de0cf276

@ -44,37 +44,7 @@ the result.
The following trigonometric binary operators, which work in radians, exist in Prometheus: The following trigonometric binary operators, which work in radians, exist in Prometheus:
* `atan2` (based on https://pkg.go.dev/math#Atan2, _This is experimental_) * `atan2` (based on https://pkg.go.dev/math#Atan2)
A usecase of `atan2` is converting directional data between the [polar](https://en.wikipedia.org/wiki/Polar_coordinate_system) (r, theta)
and [cartesian](https://en.wikipedia.org/wiki/Cartesian_coordinate_system) (x, y) coordinate forms.
Example:
Take some wind speed and direction data in the polar form. To get a trend over a
longer period of time, it's not correct to just average out the direction data.
The polar data needs to be converted into the cartesian form:
```
wind:northwards = windspeed * cos(rad(winddirection))
wind:westwards = windspeed * sin(rad(winddirection))
```
Having done that, the longerterm averages over northwards and westwards now make sense:
```
wind:northwards:avg1h = avg_over_time(wind:northwards[1h])
wind:westwards:avg1h = avg_over_time(wind:westwards[1h])
```
The "average" direction can be extracted out of these again by using `atan2`:
```
wind:direction:avg1h = deg(wind:northwards:avg1h atan2 wind:westwards:avg1h)
```
The Wikipedia article on the circular mean has more about this calculation:
https://en.wikipedia.org/wiki/Circular_mean
Trigonometric operators allow trigonometric functions to be executed on two vectors using Trigonometric operators allow trigonometric functions to be executed on two vectors using
vector matching, which isn't available with normal functions. They act in the same manner vector matching, which isn't available with normal functions. They act in the same manner

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