HistogramWithProperBarWidth.scala

trait Histo {
  def bins: Array[Int]
  def name: String
}

def mkChart(histo: Histo): XYChart = {
  val data = histo.bins.zipWithIndex.map { case (num, idx) =>
    histo.center(idx) -> num
  } .toVector
  import scalax.chart.api._

  val barWidth  = histo.center(1) - histo.center(0)
  val fihData   = data.toXYSeriesCollection(histo.name)
  val withWidth = new XYBarDataset(fihData, barWidth)
  val chart     = XYBarChart(withWidth, title = s"Histogram for ${histo.name}")
  val plot      = chart.plot
  plot.getRenderer.setSeriesPaint(0, Color.darkGray)
  chart
}