Scala简单直方图 [英] Scala simple histogram

问题描述

例如对于给定的Array[Double]

val a = Array.tabulate(100){ _ => Random.nextDouble * 10 }

使用n箱计算直方图的简单方法是什么?

what is a simple approach to calculate a histogram with n bins ?

推荐答案

与@ om-nom-nom的答案非常相似的值准备，但是使用partition的直方图方法非常小，

A very similar preparation of values as in @om-nom-nom 's answer, yet the histogram method quite small by using partition,

case class Distribution(nBins: Int, data: List[Double]) {
  require(data.length > nBins)

  val Epsilon = 0.000001
  val (max,min) = (data.max,data.min)
  val binWidth = (max - min) / nBins + Epsilon
  val bounds = (1 to nBins).map { x => min + binWidth * x }.toList

  def histo(bounds: List[Double], data: List[Double]): List[List[Double]] =
    bounds match {
      case h :: Nil => List(data)
      case h :: t   => val (l,r) = data.partition( _ < h) ; l :: histo(t,r)
    }

  val histogram = histo(bounds, data)
}

然后

val data = Array.tabulate(100){ _ => scala.util.Random.nextDouble * 10 }
val h = Distribution(5, data.toList).histogram

等等

val tabulated = h.map {_.size}

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