ST_attrFloatAverage-AnalyticDB(AnalyticDB)-阿里云帮助中心

Returns the arithmetic mean of all values in a float-type attribute field across all points in a trajectory object.

Syntax

float8 ST_attrFloatAverage(trajectory traj, cstring attr_field_name);

Parameters

Parameter	Type	Description
`traj`	`trajectory`	The trajectory object.
`attr_field_name`	`cstring`	The name of the attribute field. The field must be of `float` type in the trajectory.

Example

The following example computes the average heading value across all 16 points in a trajectory.

SELECT ST_attrFloatAverage(
  ST_makeTrajectory(
    'STPOINT'::leaftype,
    'LINESTRING(-179.48077 51.72814,-179.46731 51.74634,-179.46502 51.74934,-179.46183 51.75378,-179.45943 51.75736,-179.45560 51.76273,-179.44845 51.77186,-179.43419 51.78977,-179.41259 51.81643,-179.41001 51.81941,-179.40751 51.82223,-179.40497 51.82505,-179.40242 51.82796,-179.39981 51.83095,-179.39734 51.83398,-179.39499 51.83709)'::geometry,
    ARRAY[
      '2017-01-15 09:06:39'::timestamp, '2017-01-15 09:13:39',
      '2017-01-15 09:14:48', '2017-01-15 09:16:28',
      '2017-01-15 09:17:48', '2017-01-15 09:19:48',
      '2017-01-15 09:23:19', '2017-01-15 09:30:28',
      '2017-01-15 09:34:40', '2017-01-15 09:36:59',
      '2017-01-15 09:38:09', '2017-01-15 09:39:18',
      '2017-01-15 09:40:40', '2017-01-15 09:47:38',
      '2017-01-15 09:48:49', '2017-01-15 21:18:30'
    ],
    '{"leafcount": 16, "attributes": {"heading": {"type": "float", "length": 4, "nullable": false, "value": [23.0,23.0,23.0,23.0,21.0,21.0,72.0,72.0,72.0,72.0,73.0,74.0,73.0,73.0,73.0,73.0]}}}'
  ),
  'heading'
);

Output:

 st_attrfloataverage
---------------------
             53.8125
(1 row)