remove unintentional interpolate section (github#258)

Co-authored-by: Miranda Auhl <[email protected]>
Co-authored-by: Lana Brindley <[email protected]>

Author: mirandaauhl

api/histogram.md

@@ -48,92 +48,3 @@ The expected output:
  demo000008 | {0,0,311,345,116,228,0}
  demo000009 | {295,92,105,50,8,8,442}
 ```
-
----
-
-## interpolate() <tag type="community">Community</tag> 
-
-The `interpolate` function does linear interpolation for missing values.
-It can only be used in an aggregation query with [time_bucket_gapfill](/hyperfunctions/gapfilling-interpolation/time_bucket_gapfill/).
-The `interpolate` function call cannot be nested inside other function calls.
-
-### Required Arguments
-
-|Name|Type|Description|
-|---|---|---|
-| `value` | INTEGER | The value to interpolate (int2/int4/int8/float4/float8) |
-
-### Optional Arguments
-
-|Name|Type|Description|
-|---|---|---|
-| `prev` | RECORD | The lookup expression for values before the gapfill time range  |
-| `next` | RECORD | The lookup expression for values after the gapfill time range  |
-
-Because the interpolation function relies on having values before and after
-each bucketed period to compute the interpolated value, it might not have
-enough data to calculate the interpolation for the first and last time bucket
-if those buckets do not otherwise contain valid values.
-For example, the interpolation would require looking before this first
-time bucket period, yet the query's outer time predicate WHERE time > ...
-normally restricts the function to only evaluate values within this time range.
-Thus, the `prev` and `next` expression tell the function how to look for
-values outside of the range specified by the time predicate.
-These expressions will only be evaluated when no suitable value is returned by the outer query
-(i.e., the first and/or last bucket in the queried time range is empty).
-The returned record for `prev` and `next` needs to be a time, value tuple.
-The datatype of time needs to be the same as the time datatype in the `time_bucket_gapfill` call.
-The datatype of value needs to be the same as the `value` datatype of the `interpolate` call.
-
-### Sample Usage 
-
-Get the temperature every day for each device over the last week interpolating for missing readings:
-```sql
-SELECT
-  time_bucket_gapfill('1 day', time, now() - INTERVAL '1 week', now()) AS day,
-  device_id,
-  avg(temperature) AS value,
-  interpolate(avg(temperature))
-FROM metrics
-WHERE time > now () - INTERVAL '1 week'
-GROUP BY day, device_id
-ORDER BY day;
-
-           day          | device_id | value | interpolate
-------------------------+-----------+-------+-------------
- 2019-01-10 01:00:00+01 |         1 |       |
- 2019-01-11 01:00:00+01 |         1 |   5.0 |         5.0
- 2019-01-12 01:00:00+01 |         1 |       |         6.0
- 2019-01-13 01:00:00+01 |         1 |   7.0 |         7.0
- 2019-01-14 01:00:00+01 |         1 |       |         7.5
- 2019-01-15 01:00:00+01 |         1 |   8.0 |         8.0
- 2019-01-16 01:00:00+01 |         1 |   9.0 |         9.0
-(7 row)
-```
-
-Get the average temperature every day for each device over the last 7 days interpolating for missing readings with lookup queries for values before and after the gapfill time range:
-```sql
-SELECT
-  time_bucket_gapfill('1 day', time, now() - INTERVAL '1 week', now()) AS day,
-  device_id,
-  avg(value) AS value,
-  interpolate(avg(temperature),
-    (SELECT (time,temperature) FROM metrics m2 WHERE m2.time < now() - INTERVAL '1 week' AND m.device_id = m2.device_id ORDER BY time DESC LIMIT 1),
-    (SELECT (time,temperature) FROM metrics m2 WHERE m2.time > now() AND m.device_id = m2.device_id ORDER BY time DESC LIMIT 1)
-  ) AS interpolate
-FROM metrics m
-WHERE time > now () - INTERVAL '1 week'
-GROUP BY day, device_id
-ORDER BY day;
-
-           day          | device_id | value | interpolate
-------------------------+-----------+-------+-------------
- 2019-01-10 01:00:00+01 |         1 |       |         3.0
- 2019-01-11 01:00:00+01 |         1 |   5.0 |         5.0
- 2019-01-12 01:00:00+01 |         1 |       |         6.0
- 2019-01-13 01:00:00+01 |         1 |   7.0 |         7.0
- 2019-01-14 01:00:00+01 |         1 |       |         7.5
- 2019-01-15 01:00:00+01 |         1 |   8.0 |         8.0
- 2019-01-16 01:00:00+01 |         1 |   9.0 |         9.0
-(7 row)
-```