Sample collection handling

gistfile1.scala

// This is a sample of handling collections with Scala
// It receives the .xml from your delicious account and generates an output to plot 
// the count of tags on a timeframe
//
// Please, if you know better ways to do the same processing, please let me know: @arjones
//

import scala.xml._
import org.joda.time._

object App {
  
  def main(args: Array[String]) = {
    
    // curl https://USERNAME:PASSWORD@api.del.icio.us/v1/posts/all > data/data.xml
    //
    val delicious = XML.loadFile("data/data.xml")
    val dateAndTags = extractDateAndTags(delicious)

     //group tags by month
    val tagsByMonth = dateAndTags.groupBy(groupByInstruction)

    // grouping together the tags 
    val flattenTagsByMonth = tagsByMonth.map(e => (e._1, e._2.map(_._2).flatten))

    // Map[DateTime, Map[String,Int]]
    // Date -> (Tag, Count)
    //
    val dateTagCount = flattenTagsByMonth.map { el =>
      val key: DateTime = el._1
      val values: Seq[String] = el._2

      val valuesCount = values.groupBy(e => e)

      val tagCount = valuesCount.map(e => (e._1, e._2.size))
      (key, tagCount)
    }

    // create a index of keys sorted to print out correctly
    val dates = dateTagCount.keys.toList.sortWith((a, b) => b.isAfter(a))

    // get tags that appear more than XX times per month
    val MIN_APPEARS = 4
    val relevantTags = dateTagCount.values.flatten.filter(_._2 > MIN_APPEARS).map(_._1).toList.distinct.filterNot(_ == "").sortWith((a, b) => a < b)

    printResults(dates, relevantTags, dateTagCount)
  }

  def extractDateAndTags(doc: Elem) = {
    (doc \\ "post").map { p =>
      val date = p.attribute("time").getOrElse("1970-01-01").toString
      val tags = p.attribute("tag").getOrElse("").toString.toLowerCase.split(" ")

      (new DateTime(date), tags.filterNot(_ == "for:@twitter"))
    }
  }

  // this function group by month
  def groupByInstruction(e: (DateTime, Array[String])) = e._1.monthOfYear.roundFloorCopy()

  def printResults(dates: List[DateTime], relevantTags: List[String], dateTagCount: Map[DateTime, Map[String, Int]]) {
    // print results
    // headers
    print("date\t")
    for (tag <- relevantTags) print(tag + "\t")
    println()

    // each element
    for (date <- dates) {
      print(date.toLocalDate() + "\t")

      val tag = dateTagCount(date)

      for (h <- relevantTags) {
        val count = if (tag.contains(h)) tag(h) else ""
        print(count + "\t")
      }
      println()
    }
  }
}