{"action":"created","comment":{"url":"https://api.github.com/repos/apache/spark/pulls/comments/37246859","id":37246859,"diff_hunk":"@@ -649,6 +649,70 @@ for expanded in polyDF.select(\"polyFeatures\").take(3):\n </div>\n </div>\n \n+## Discrete Cosine Transform (DCT)\n+\n+The [Discrete Cosine Transform](https://en.wikipedia.org/wiki/Discrete_cosine_transform) transforms a length $N$ real-valued sequence in the time domain into another length $N$ real-valued sequence in the frequency domain. A [DCT](api/scala/index.html#org.apache.spark.ml.feature.DCT) class provides this functionality, implementing the [DCT-II](https://en.wikipedia.org/wiki/Discrete_cosine_transform#DCT-II) and scaling the result by $1/\\sqrt{2}$ such that the representing matrix for the transform is unitary. No shift is applied to the transformed sequence (e.g. the $0$th element of the transformed sequence is the $0$th DCT coefficient and _not_ the $N/2$th).\n+\n+<div class=\"codetabs\">\n+<div data-lang=\"scala\" markdown=\"1\">\n+{% highlight scala %}\n+import org.apache.spark.ml.feature.DCT\n+import org.apache.spark.mllib.linalg.Vectors\n+\n+val data = Seq(\n+  Vectors.dense(0.0, 1.0, -2.0, 3.0),\n+  Vectors.dense(-1.0, 2.0, 4.0, -7.0),\n+  Vectors.dense(14.0, -2.0, -5.0, 1.0))\n+val df = sqlContext.createDataFrame(data.map(Tuple1.apply)).toDF(\"features\")\n+val DCTransform = new DCT()\n+  .setInputCol(\"features\")\n+  .setOutputCol(\"featuresDCT\")\n+  .setInverse(false)\n+val DCTdf = DCTransform.transform(df)","path":"docs/ml-features.md","position":23,"original_position":23,"commit_id":"027fbf0989b428e6ecc8d891a9083550a5d3656b","original_commit_id":"027fbf0989b428e6ecc8d891a9083550a5d3656b","user":{"login":"mengxr","id":829644,"avatar_url":"https://avatars.githubusercontent.com/u/829644?v=3","gravatar_id":"","url":"https://api.github.com/users/mengxr","html_url":"https://github.com/mengxr","followers_url":"https://api.github.com/users/mengxr/followers","following_url":"https://api.github.com/users/mengxr/following{/other_user}","gists_url":"https://api.github.com/users/mengxr/gists{/gist_id}","starred_url":"https://api.github.com/users/mengxr/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/mengxr/subscriptions","organizations_url":"https://api.github.com/users/mengxr/orgs","repos_url":"https://api.github.com/users/mengxr/repos","events_url":"https://api.github.com/users/mengxr/events{/privacy}","received_events_url":"https://api.github.com/users/mengxr/received_events","type":"User","site_admin":false},"body":"`DCTdf` -> `dctDf`","created_at":"2015-08-17T22:54:21Z","updated_at":"2015-08-17T22:54:21Z","html_url":"https://github.com/apache/spark/pull/8184#discussion_r37246859","pull_request_url":"https://api.github.com/repos/apache/spark/pulls/8184","_links":{"self":{"href":"https://api.github.com/repos/apache/spark/pulls/comments/37246859"},"html":{"href":"https://github.com/apache/spark/pull/8184#discussion_r37246859"},"pull_request":{"href":"https://api.github.com/repos/apache/spark/pulls/8184"}}},"pull_request":{"url":"https://api.github.com/repos/apache/spark/pulls/8184","id":42417247,"html_url":"https://github.com/apache/spark/pull/8184","diff_url":"https://github.com/apache/spark/pull/8184.diff","patch_url":"https://github.com/apache/spark/pull/8184.patch","issue_url":"https://api.github.com/repos/apache/spark/issues/8184","number":8184,"state":"open","locked":false,"title":"[SPARK-8473][SPARK-9889][ML] User guide and example code for 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