[DOCS] Creates a data frame examples page (#389)

This PR creates a data frame examples page under data-frames and indicates it in the index file.

docs/en/stack/data-frames/dataframe-examples.asciidoc

@@ -0,0 +1,340 @@
+[role="xpack"]
+[testenv="basic"]
+[[dataframe-examples]]
+== {dataframe-cap} examples
+++++
+<titleabbrev>Examples</titleabbrev>
+++++
+
+beta[]
+
+These examples demonstrate how to use {dataframe-transforms} to derive useful 
+insights from your data. All the examples use one of the 
+{kibana-ref}/add-sample-data.html[{kib} sample datasets]. For a more detailed, 
+step-by-step example, see 
+<<ecommerce-dataframes,Transforming your data with {dataframes}>>.
+
+* <<example-best-customers>>
+* <<example-airline>>
+* <<example-clientips>>
+
+[float]
+[[example-best-customers]]
+=== Finding your best customers
+
+In this example, we use the eCommerce orders sample dataset to find the customers 
+who spent the most in our hypothetical webshop. Let's transform the data such 
+that the destination index contains the number of orders, the total price of 
+the orders, the amount of unique products and the average price per order, 
+and the total amount of ordered products for each customer.
+
+[source,js]
+----------------------------------
+POST _data_frame/transforms/_preview
+{
+  "source": {
+    "index": "kibana_sample_data_ecommerce"
+  },
+  "dest" : { <1>
+    "index" : "sample_ecommerce_orders_by_customer"
+  },
+  "pivot": {
+    "group_by": { <2>
+      "user": { "terms": { "field": "user" }}, 
+      "customer_id": { "terms": { "field": "customer_id" }}
+    },
+    "aggregations": {
+      "order_count": { "value_count": { "field": "order_id" }},
+      "total_order_amt": { "sum": { "field": "taxful_total_price" }},
+      "avg_amt_per_order": { "avg": { "field": "taxful_total_price" }},
+      "avg_unique_products_per_order": { "avg": { "field": "total_unique_products" }},
+      "total_unique_products": { "cardinality": { "field": "products.product_id" }}
+    }
+  }
+}
+----------------------------------
+// CONSOLE
+// TEST[skip:SETUP]
+
+<1> This is the destination index for the {dataframe}. It is ignored by 
+`_preview`.
+<2> Two `group_by` fields have been selected. This means the {dataframe} will 
+contain a unique row per `user` and `customer_id` combination. Within this 
+dataset both these fields are unique. By including both in the {dataframe} it 
+gives more context to the final results.
+
+NOTE: In the example above, condensed JSON formatting has been used for easier 
+readability of the pivot object.
+
+The preview {dataframe-transforms} API enables you to see the layout of the 
+{dataframe} in advance, populated with some sample values. For example:
+
+[source,js]
+----------------------------------
+{
+  "preview" : [
+    {
+      "total_order_amt" : 3946.9765625,
+      "order_count" : 59.0,
+      "total_unique_products" : 116.0,
+      "avg_unique_products_per_order" : 2.0,
+      "customer_id" : "10",
+      "user" : "recip",
+      "avg_amt_per_order" : 66.89790783898304
+    },
+    ...
+    ]
+  }
+----------------------------------
+// CONSOLE
+// TEST[skip:SETUP]
+
+This {dataframe} makes it easier to answer questions such as:
+
+* Which customers spend the most?
+
+* Which customers spend the most per order?
+
+* Which customers order most often?
+
+* Which customers ordered the least number of different products?
+
+It's possible to answer these questions using aggregations alone, however 
+{dataframes} allow us to persist this data as a customer centric index. This 
+enables us to analyze data at scale and gives more flexibility to explore and 
+navigate data from a customer centric perspective. In some cases, it can even 
+make creating visualizations much simpler.
+
+[float]
+[[example-airline]]
+=== Finding air carriers with the most delays
+
+In this example, we use the Flights sample dataset to find out which air carrier 
+had the most delays. First, we filter the source data such that it excludes all 
+the cancelled flights by using a query filter. Then we transform the data to 
+contain the distinct number of flights, the sum of delayed minutes, and the sum 
+of the flight minutes by air carrier. Finally, we use a 
+{ref}/search-aggregations-pipeline-bucket-script-aggregation.html[`bucket_script`] 
+to determine what percentage of the flight time was actually delay.
+
+[source,js]
+----------------------------------
+POST _data_frame/transforms/_preview
+{
+  "source": {
+    "index": "kibana_sample_data_flights",
+    "query": { <1>
+      "bool": {
+        "filter": [
+          { "term":  { "Cancelled": false } }
+        ]
+      }
+    }
+  },
+  "dest" : { <2>
+    "index" : "sample_flight_delays_by_carrier"
+  },
+  "pivot": {
+    "group_by": { <3>
+      "carrier": { "terms": { "field": "Carrier" }}
+    },
+    "aggregations": {
+      "flights_count": { "value_count": { "field": "FlightNum" }},
+      "delay_mins_total": { "sum": { "field": "FlightDelayMin" }},
+      "flight_mins_total": { "sum": { "field": "FlightTimeMin" }},
+      "delay_time_percentage": { <4>
+        "bucket_script": {
+          "buckets_path": {
+            "delay_time": "delay_mins_total.value",
+            "flight_time": "flight_mins_total.value"
+          },
+          "script": "(params.delay_time / params.flight_time) * 100"
+        }
+      }
+    }
+  }
+}
+----------------------------------
+// CONSOLE
+// TEST[skip:SETUP]
+
+<1> Filter the source data to select only flights that were not cancelled.
+<2> This is the destination index for the {dataframe}. It is ignored by 
+`_preview`.
+<3> The data is grouped by the `Carrier` field which contains the airline name.
+<4> This `bucket_script` performs calculations on the results that are returned 
+by the aggregation. In this particular example, it calculates what percentage of 
+travel time was taken up by delays.
+
+The preview shows you that the new index would contain data like this for each 
+carrier:
+
+[source,js]
+----------------------------------
+{
+  "preview" : [
+    {
+      "carrier" : "ES-Air",
+      "flights_count" : 2802.0,
+      "flight_mins_total" : 1436927.5130677223,
+      "delay_time_percentage" : 9.335543983955839,
+      "delay_mins_total" : 134145.0
+    },
+    ...
+  ]
+}
+----------------------------------
+// CONSOLE
+// TEST[skip:SETUP]
+
+This {dataframe} makes it easier to answer questions such as:
+
+* Which air carrier has the most delays as a percentage of flight time?
+
+NOTE: This data is fictional and does not reflect actual delays 
+or flight stats for any of the featured destination or origin airports.
+
+[float]
+[[example-clientips]]
+=== Finding suspicious client IPs by using scripted metrics
+
+With {dataframe-transforms}, you can use 
+{ref}/search-aggregations-metrics-scripted-metric-aggregation.html[scripted 
+metric aggregations] on your data. These aggregations are flexible and make 
+it possible to perform very complex processing. Let's use scripted metrics to 
+identify suspicious client IPs in the web log sample dataset.
+
+We transform the data such that the new index contains the sum of bytes and the 
+number of distinct URLs, agents, incoming requests by location, and geographic 
+destinations for each client IP. We also use a scripted field to count the 
+specific types of HTTP responses that each client IP receives. Ultimately, the 
+example below transforms web log data into an entity centric index where the 
+entity is `clientip`.
+
+[source,js]
+----------------------------------
+POST _data_frame/transforms/_preview
+{
+  "source": {
+    "index": "kibana_sample_data_logs",
+    "query": { <1>
+      "range" : {
+        "timestamp" : {
+          "gte" : "now-30d/d"
+        }
+      }
+    }
+  },
+  "dest" : { <2>
+    "index" : "sample_weblogs_by_clientip"
+  },  
+  "pivot": {
+    "group_by": {  <3>
+      "clientip": { "terms": { "field": "clientip" } }
+      },
+    "aggregations": {
+      "url_dc": { "cardinality": { "field": "url.keyword" }},
+      "bytes_sum": { "sum": { "field": "bytes" }},
+      "geo.src_dc": { "cardinality": { "field": "geo.src" }},
+      "agent_dc": { "cardinality": { "field": "agent.keyword" }},
+      "geo.dest_dc": { "cardinality": { "field": "geo.dest" }},
+      "responses.total": { "value_count": { "field": "timestamp" }},
+      "responses.counts": { <4>
+        "scripted_metric": { 
+          "init_script": "state.responses = ['error':0L,'success':0L,'other':0L]",
+          "map_script": """
+            def code = doc['response.keyword'].value;
+            if (code.startsWith('5') || code.startsWith('4')) {
+              state.responses.error += 1 ;
+            } else if(code.startsWith('2')) {
+              state.responses.success += 1;
+            } else {
+              state.responses.other += 1;
+            }
+            """,
+          "combine_script": "state.responses",
+          "reduce_script": """
+            def counts = ['error': 0L, 'success': 0L, 'other': 0L];
+            for (responses in states) {
+              counts.error += responses['error'];
+              counts.success += responses['success'];
+              counts.other += responses['other'];
+            }
+            return counts;
+            """
+          }
+        },
+      "timestamp.min": { "min": { "field": "timestamp" }},
+      "timestamp.max": { "max": { "field": "timestamp" }},
+      "timestamp.duration_ms": { <5>
+        "bucket_script": {
+          "buckets_path": {
+            "min_time": "timestamp.min.value",
+            "max_time": "timestamp.max.value"
+          },
+          "script": "(params.max_time - params.min_time)"
+        }
+      }
+    }
+  }
+}
+----------------------------------
+// CONSOLE
+// TEST[skip:SETUP]
+
+<1> This range query limits the transform to documents that are within the last 
+30 days at the point in time the {dataframe-transform} checkpoint is processed. 
+For batch {dataframes} this occurs once.
+<2> This is the destination index for the {dataframe}. It is ignored by 
+`_preview`.
+<3> The data is grouped by the `clientip` field. 
+<4> This `scripted_metric` performs a distributed operation on the web log data 
+to count specific types of HTTP responses (error, success, and other).
+<5> This `bucket_script` calculates the duration of the `clientip` access based 
+on the results of the aggregation.
+
+The preview shows you that the new index would contain data like this for each 
+client IP:
+
+[source,js]
+----------------------------------
+{
+  "preview" : [
+    {
+      "geo" : {
+        "src_dc" : 12.0,
+        "dest_dc" : 9.0
+      },
+      "clientip" : "0.72.176.46",
+      "agent_dc" : 3.0,
+      "responses" : {
+        "total" : 14.0,
+        "counts" : {
+          "other" : 0,
+          "success" : 14,
+          "error" : 0
+        }
+      },
+      "bytes_sum" : 74808.0,
+      "timestamp" : {
+        "duration_ms" : 4.919943239E9,
+        "min" : "2019-06-17T07:51:57.333Z",
+        "max" : "2019-08-13T06:31:00.572Z"
+      },
+      "url_dc" : 11.0
+    },
+    ...
+  }
+----------------------------------  
+// CONSOLE
+// TEST[skip:SETUP]
+
+This {dataframe} makes it easier to answer questions such as:
+
+* Which client IPs are transferring the most amounts of data?
+
+* Which client IPs are interacting with a high number of different URLs?
+
+* Which client IPs have high error rates?
+
+* Which client IPs are interacting with a high number of destination countries?

docs/en/stack/data-frames/index.asciidoc

@@ -1,3 +1,4 @@
 include::dataframes.asciidoc[]
 include::ecommerce-example.asciidoc[]
-include::api-quickref.asciidoc[]
+include::api-quickref.asciidoc[]
+include::dataframe-examples.asciidoc[]