From 62bb691c65dc18fcc75e07bc93198ac3435f8d29 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mantas=20Marcinkevi=C4=8Dius?= <marc.mantas@gmail.com>
Date: Mon, 29 Aug 2016 15:48:20 +0300
Subject: [PATCH] added documentation
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.../Pipeline/SerialDifferencing.md | 54 +++++++++++++++++++
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+# Serial Differencing Aggregation
+
+> More info about serial differencing aggregation is in the [official elasticsearch docs][1]
+
+Serial differencing is a technique where values in a time series are subtracted from itself at
+different time lags or periods
+
+## Simple example
+
+```JSON
+{
+ "aggs": {
+ "my_date_histo": {
+ "date_histogram": {
+ "field": "timestamp",
+ "interval": "day"
+ },
+ "aggs": {
+ "the_sum": {
+ "sum": {
+ "field": "lemmings"
+ }
+ },
+ "thirtieth_difference": {
+ "serial_diff": {
+ "buckets_path": "the_sum",
+ "lag" : 30
+ }
+ }
+ }
+ }
+ }
+}
+```
+
+And now the query via DSL:
+
+```php
+$search = new Search();
+
+$dateAggregation = new DateHistogramAggregation('my_date_histo', 'timestamp', 'day');
+$dateAggregation->addAggregation(
+ new SumAggregation('the_sum', 'lemmings')
+);
+$diffAggregation = new SerialDifferencingAggregation('thirtieth_difference', 'the_sum');
+$diffAggregation->addParameter('lag', 30);
+$dateAggregation->addAggregation($diffAggregation);
+
+$search->addAggregation($dateAggregation);
+
+$aggArray = $search->toArray();
+```
+
+[1]: https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-pipeline-serialdiff-aggregation.html
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