OpenSearch/docs/reference/aggregations/metrics/geocentroid-aggregation.asciidoc
Christoph Büscher 16a7cbe463 Add count value to rest output of geo_centroid (#24387)
Currently we don't write the count value to the geo_centroid aggregation rest response,
but it is provided via the java api and the count() method in the GeoCentroid interface. 
We should add this parameter to the rest output and also provide it via the getProperty()
method.
2017-04-28 16:25:22 +02:00

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[[search-aggregations-metrics-geocentroid-aggregation]]
=== Geo Centroid Aggregation
A metric aggregation that computes the weighted https://en.wikipedia.org/wiki/Centroid[centroid] from all coordinate values for a <<geo-point>> field.
Example:
[source,js]
--------------------------------------------------
PUT /museums
{
"mappings": {
"doc": {
"properties": {
"location": {
"type": "geo_point"
}
}
}
}
}
POST /museums/doc/_bulk?refresh
{"index":{"_id":1}}
{"location": "52.374081,4.912350", "city": "Amsterdam", "name": "NEMO Science Museum"}
{"index":{"_id":2}}
{"location": "52.369219,4.901618", "city": "Amsterdam", "name": "Museum Het Rembrandthuis"}
{"index":{"_id":3}}
{"location": "52.371667,4.914722", "city": "Amsterdam", "name": "Nederlands Scheepvaartmuseum"}
{"index":{"_id":4}}
{"location": "51.222900,4.405200", "city": "Antwerp", "name": "Letterenhuis"}
{"index":{"_id":5}}
{"location": "48.861111,2.336389", "city": "Paris", "name": "Musée du Louvre"}
{"index":{"_id":6}}
{"location": "48.860000,2.327000", "city": "Paris", "name": "Musée d'Orsay"}
POST /museums/_search?size=0
{
"aggs" : {
"centroid" : {
"geo_centroid" : {
"field" : "location" <1>
}
}
}
}
--------------------------------------------------
// CONSOLE
<1> The `geo_centroid` aggregation specifies the field to use for computing the centroid. (NOTE: field must be a <<geo-point>> type)
The above aggregation demonstrates how one would compute the centroid of the location field for all documents with a crime type of burglary
The response for the above aggregation:
[source,js]
--------------------------------------------------
{
...
"aggregations": {
"centroid": {
"location": {
"lat": 51.00982963107526,
"lon": 3.9662130922079086
},
"count": 6
}
}
}
--------------------------------------------------
// TESTRESPONSE[s/\.\.\./"took": $body.took,"_shards": $body._shards,"hits":$body.hits,"timed_out":false,/]
The `geo_centroid` aggregation is more interesting when combined as a sub-aggregation to other bucket aggregations.
Example:
[source,js]
--------------------------------------------------
POST /museums/_search?size=0
{
"aggs" : {
"cities" : {
"terms" : { "field" : "city.keyword" },
"aggs" : {
"centroid" : {
"geo_centroid" : { "field" : "location" }
}
}
}
}
}
--------------------------------------------------
// CONSOLE
// TEST[continued]
The above example uses `geo_centroid` as a sub-aggregation to a
<<search-aggregations-bucket-terms-aggregation, terms>> bucket aggregation
for finding the central location for museums in each city.
The response for the above aggregation:
[source,js]
--------------------------------------------------
{
...
"aggregations": {
"cities": {
"sum_other_doc_count": 0,
"doc_count_error_upper_bound": 0,
"buckets": [
{
"key": "Amsterdam",
"doc_count": 3,
"centroid": {
"location": {
"lat": 52.371655656024814,
"lon": 4.909563297405839
},
"count": 3
}
},
{
"key": "Paris",
"doc_count": 2,
"centroid": {
"location": {
"lat": 48.86055548675358,
"lon": 2.3316944623366
},
"count": 2
}
},
{
"key": "Antwerp",
"doc_count": 1,
"centroid": {
"location": {
"lat": 51.22289997059852,
"lon": 4.40519998781383
},
"count": 1
}
}
]
}
}
}
--------------------------------------------------
// TESTRESPONSE[s/\.\.\./"took": $body.took,"_shards": $body._shards,"hits":$body.hits,"timed_out":false,/]