title: Scala Spark : Convert Double Column to Date Time Column in dataframe
body: <p>I am trying to write code to convert date-time columns date and last_updated_date which are actually unix times cast as doubles into "mm-dd-yyyy" format for display. How do I do this ?</p>
  
  <pre><code>import org.joda.time._
  import scala.tools._
  import org.joda.time.format.DateTimeFormat._
  import java.text.SimpleDateFormat
  import org.apache.spark.sql.functions.{unix_timestamp, to_date}
  root
   |-- date: double (nullable = false)
   |-- last_updated_date: double (nullable = false)
   |-- Percent_Used: double (nullable = false)
  
  +------------+---------------------+------------+
  |        date|    last_updated_date|Percent_Used|
  +------------+---------------------+------------+
  | 1.453923E12|        1.47080394E12| 1.948327124|
  |1.4539233E12|        1.47080394E12| 2.019636442|
  |1.4539236E12|        1.47080394E12| 1.995299371|
  +------------+---------------------+------------+
  </code></pre>