port interpolate pkg from flux-restructure branch, closes #2414 (#2467)

content/influxdb/cloud/reference/flux/stdlib/interpolate/_index.md

@@ -0,0 +1,15 @@
+---
+title: Flux interpolate package
+list_title: Interpolate package
+description: >
+  The Flux `interpolate` package provides functions that insert rows for missing
+  data at regular intervals and estimate values using different interpolation methods.
+  Import the `interpolate` package.
+menu:
+  influxdb_cloud_ref:
+    name: Interpolate
+    parent: Flux standard library
+weight: 202
+---
+
+{{< duplicate-oss >}}

content/influxdb/cloud/reference/flux/stdlib/interpolate/linear.md

@@ -0,0 +1,15 @@
+---
+title: interpolate.linear() function
+description: >
+  The `interpolate.linear` function inserts rows at regular intervals using
+  **linear interpolation** to determine values for inserted rows.
+menu:
+  influxdb_cloud_ref:
+    name: interpolate.linear
+    parent: Interpolate
+weight: 301
+introduced: 0.87.0
+list_query_example: interpolate_linear
+---
+
+{{< duplicate-oss >}}

content/influxdb/v2.0/reference/flux/stdlib/interpolate/_index.md

@@ -0,0 +1,23 @@
+---
+title: Flux interpolate package
+list_title: Interpolate package
+description: >
+  The Flux `interpolate` package provides functions that insert rows for missing
+  data at regular intervals and estimate values using different interpolation methods.
+  Import the `interpolate` package.
+menu:
+  influxdb_2_0_ref:
+    name: Interpolate
+    parent: Flux standard library
+weight: 202
+---
+
+The `interpolate` package provides functions that insert rows for missing
+data at regular intervals and estimate values using different interpolation methods.
+Import the `interpolate` package:
+
+```js
+import "interpolate"
+```
+
+{{< children type="articles" show="pages" >}}

content/influxdb/v2.0/reference/flux/stdlib/interpolate/linear.md

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+---
+title: interpolate.linear() function
+description: >
+  The `interpolate.linear` function inserts rows at regular intervals using
+  **linear interpolation** to determine values for inserted rows.
+menu:
+  influxdb_2_0_ref:
+    name: interpolate.linear
+    parent: Interpolate
+weight: 301
+introduced: 0.87.0
+list_query_example: interpolate_linear
+---
+
+The `interpolate.linear` function inserts rows at regular intervals using
+[linear interpolation](https://en.wikipedia.org/wiki/Linear_interpolation)
+to determine values for inserted rows.
+
+```js
+import "interpolate"
+
+interpolate.linear(every: 1m)
+```
+
+#### Function requirements
+- Input data must have `_time` and `_value` columns.
+- **All columns** other than `_time` and `_value` must be part of the group key.
+
+## Parameters
+
+### every
+Duration of time between interpolated points.
+
+_**Data type:** Duration_
+
+## Examples
+
+### Interpolate missing data by day
+```js
+import "interpolate"
+
+data
+  |> interpolate.linear(every: 1d)
+```
+
+{{< flex >}}
+{{% flex-content %}}
+##### Input
+| _time                | _value |
+|:-----                | ------:|
+| 2021-01-01T00:00:00Z | 10.0   |
+| 2021-01-02T00:00:00Z | 20.0   |
+| 2021-01-04T00:00:00Z | 40.0   |
+| 2021-01-05T00:00:00Z | 50.0   |
+| 2021-01-08T00:00:00Z | 80.0   |
+| 2021-01-09T00:00:00Z | 90.0   |
+{{% /flex-content %}}
+{{% flex-content %}}
+##### Output
+| _time                | _value |
+|:-----                | ------:|
+| 2021-01-01T00:00:00Z | 10.0   |
+| 2021-01-02T00:00:00Z | 20.0   |
+| 2021-01-04T00:00:00Z | 40.0   |
+| 2021-01-05T00:00:00Z | 50.0   |
+| 2021-01-06T00:00:00Z | 60.0   |
+| 2021-01-07T00:00:00Z | 70.0   |
+| 2021-01-08T00:00:00Z | 80.0   |
+| 2021-01-09T00:00:00Z | 90.0   |
+{{% /flex-content %}}
+{{< /flex >}}