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upated holtWinters doc to address PR feedback

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Scott Anderson 2019-08-06 16:36:46 -06:00
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content/v2.0/reference/flux/functions/built-in/transformations/aggregates/holtwinters.md
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@ -36,24 +36,25 @@ values six minutes apart.
#### Seasonality
[`seasonality`](#seasonality) delimits the length of a seasonal pattern according to `interval`.
If your `interval` is `2m` and `s` is `3`, then the seasonal pattern occurs every
six minutes or every three data points.
If there is no seasonality in the data, set `seasonality` to `0`.
If your `interval` is `2m` and `seasonality` is `4`, then the seasonal pattern occurs every
eight minutes or every four data points.
If data doesn't have a seasonal pattern, set `seasonality` to `0`.
#### Space values evenly in time
`holtWinters()` expects values evenly spaced in time.
To ensure this, it applies the following rules:
To ensure `holtWinters()` values are spaced evenly in time, the following rules apply:
- `interval` is used to divide the into buckets based time.
- Data is grouped into time-based "buckets" determined by the `interval`.
- If a bucket includes many values, the first value is used.
- If a bucket includes no values, a missing value (`null`) is added for that bucket.
By default, `holtWinters()` uses the first value in each time bucket.
Use [`window()`](/v2.0/reference/flux/functions/built-in/transformations/window/)
and [selectors](/v2.0/reference/flux/functions/built-in/transformations/selectors/)
or [aggregates](/v2.0/reference/flux/functions/built-in/transformations/aggregates/),
or use [`aggregateWindow()`](/v2.0/reference/flux/functions/built-in/transformations/aggregates/aggregatewindow)
to specify other values to use in the `holtWinters()` calculation.
By default, `holtWinters()` uses the first value in each time bucket to run the Holt-Winters calculation.
To specify other values to use in the calculation, use:
- [`window()`](/v2.0/reference/flux/functions/built-in/transformations/window/)
with [selectors](/v2.0/reference/flux/functions/built-in/transformations/selectors/)
or [aggregates](/v2.0/reference/flux/functions/built-in/transformations/aggregates/)
- [`aggregateWindow()`](/v2.0/reference/flux/functions/built-in/transformations/aggregates/aggregatewindow)
#### Fitted model
The `holtWinters()` function applies the [Nelder-Mead optimization](https://en.wikipedia.org/wiki/Nelder%E2%80%93Mead_method)
@ -65,7 +66,6 @@ to include "fitted" data points in results when [`withFit`](#withfit) is set to
#### Null values
`holtWinters()` treats `null` values as missing data points and includes them in the Holt-Winters calculation.
## Parameters
### n