title: Converting Spark Dataframe(with WrappedArray) to RDD[labelPoint] in scala
body: <p>I am new to Scala and I want to convert dataframe to rdd. let the  <strong>label, features</strong> convert to <code>RDD[labelPoint]</code> for the input of MLlib. But I can't find out the way to deal with <code>WrappedArray</code>.</p>
  
  <pre><code>scala&gt; test.printSchema
  root
   |-- user_id: long (nullable = true)
   |-- brand_store_sn: string (nullable = true)
   |-- label: integer (nullable = true)
   |-- money_score: double (nullable = true)
   |-- normal_score: double (nullable = true)
   |-- action_score: double (nullable = true)
   |-- features: array (nullable = true)
   |    |-- element: string (containsNull = true)
   |-- flag: string (nullable = true)
   |-- dt: string (nullable = true)
  
  
  scala&gt; test.head
  res21: org.apache.spark.sql.Row = [2533,10005072,1,2.0,1.0,1.0,WrappedArray(["d90_pv_1sec:1.4471580313422192", "d3_pv_1sec:0.9030899869919435", "d7_pv_1sec:0.9030899869919435", "d30_pv_1sec:1.414973347970818", "d90_pv_week_decay:1.4235871662780681", "d1_pv_1sec:0.9030899869919435", "d120_pv_1sec:1.4471580313422192"]),user_positive,20161130]
  </code></pre>