Added the geo_centroid aggregation

CHANGELOG.md

@@ -9,7 +9,7 @@ All notable changes to this project will be documented in this file based on the
 ### Bugfixes
 
 ### Added
-
+- `Elastica\Aggregations\GeoCentroid`
 ### Improvements
 - `Elastica\Exception\InvalidException` will be thrown if you try using an
   `Elastica\Aggregation\AbstractSimpleAggregation` without setting either the

lib/Elastica/Aggregation/GeoCentroid.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace Elastica\Aggregation;
+
+use Elastica\Exception\InvalidException;
+
+/**
+ * Class GeoCentroid.
+ *
+ * @link https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-metrics-geocentroid-aggregation.html
+ */
+class GeoCentroid extends AbstractAggregation
+{
+    /**
+     * @param string $name  the name of this aggregation
+     * @param string $field the field on which to perform this aggregation
+     */
+    public function __construct($name, $field)
+    {
+        parent::__construct($name);
+        $this->setField($field);
+    }
+
+    /**
+     * Set the field for this aggregation.
+     *
+     * @param string $field the name of the document field on which to perform this aggregation
+     *
+     * @return $this
+     */
+    public function setField($field)
+    {
+        return $this->setParam('field', $field);
+    }
+}

test/lib/Elastica/Test/Aggregation/GeoCentroidTest.php

@@ -0,0 +1,45 @@
+<?php
+namespace Elastica\Test\Aggregation;
+
+use Elastica\Aggregation\GeoCentroid;
+use Elastica\Document;
+use Elastica\Query;
+use Elastica\Type\Mapping;
+
+class GeoCentroidTest extends BaseAggregationTest
+{
+    protected function _getIndexForTest()
+    {
+        $index = $this->_createIndex();
+        $type = $index->getType('test');
+
+        $type->setMapping(new Mapping(null, array(
+            'location' => array('type' => 'geo_point'),
+        )));
+
+        $type->addDocuments(array(
+            new Document(1, array('location' => array('lat' => 32.849437, 'lon' => -117.271732))),
+            new Document(2, array('location' => array('lat' => 32.798320, 'lon' => -117.246648))),
+            new Document(3, array('location' => array('lat' => 37.782439, 'lon' => -122.392560))),
+        ));
+
+        $index->refresh();
+
+        return $index;
+    }
+
+    /**
+     * @group functional
+     */
+    public function testGeohashGridAggregation()
+    {
+        $agg = new GeoCentroid('centroid', 'location');
+
+        $query = new Query();
+        $query->addAggregation($agg);
+        $results = $this->_getIndexForTest()->search($query)->getAggregation('centroid');
+
+        $this->assertEquals(34.476731875911, $results['location']['lat']);
+        $this->assertEquals(-118.97031342611, $results['location']['lon']);
+    }
+}