Polygon cursor

function pointInsidePolygon(
  horizontalCoordinate,
  verticalCoordinate,
  h,
  v
) {
  let insideCount = 0
  let outsideCount = 0

let vertexCount = horizontalCoordinate.length

let J = vertexCount - 1
  let even = false

for (let I = 0; I < vertexCount; I++) {
    let polyI0 = horizontalCoordinate[I]
    let polyI1 = verticalCoordinate[I]
    let polyJ0 = horizontalCoordinate[J]
    let polyJ1 = verticalCoordinate[J]
    if (
      polyI1 > v !== polyJ1 > v &&
      h <
        polyI0 + ((polyJ0 - polyI0) * (v - polyI1)) / (polyJ1 - polyI1)
    ) {
      even = !even
    }
    J = I
  }

return even // even means: the point (h, v) is inside
}

kontrast.addEventListener('load', function() {
  let figure = kontrast.createFigure({
    element: 'figure0'
  })

let count = 100
  let xPointList = new Float64Array(count)
  let yPointList = new Float64Array(count)
  let cPointList = new Float64Array(count)

for (let i = 0; i < count; i++) {
    xPointList[i] = Math.random()
    yPointList[i] = Math.random()
  }

let graph = figure.createGraph({
    abscissae: { x: { yOrigin: -1 } },
    ordinates: { y: { xOrigin: -1 } },
    colorAxes: {
      c: {
        hidden: true,
        excludeFromLayout: true,
        colorBelow: 'red',
        color0: 'red',
        color1: 'blue',
        colorAbove: 'blue',
        min: 0,
        max: 1
      }
    }
  })

let pointPlot = graph.createPoints({
    color: 'blue',
    thickness: 9,
    opacity: 0.8,
    data: {
      x: xPointList,
      y: yPointList,
      c: cPointList
    }
  })

let cursor0 = graph.createCursor({
    color: 'blue',
    thickness: 9,
    opacity: 0.8,
    data: {
      x: [0.1, 0.2, 0.7, 0.6],
      y: [0.5, 0.1, 0.2, 0.6]
    }
  })

let xAverageElement = document.getElementById('x-average')
  let yAverageElement = document.getElementById('y-average')

let xAverage
  let yAverage
  let averageCount

update()

cursor0.data.addEventListener('change', update)

function update() {
    xAverage = 0
    yAverage = 0
    averageCount = 0

for (let i = 0; i < count; i++) {
      if (
        pointInsidePolygon(
          cursor0.data.value.x,
          cursor0.data.value.y,
          xPointList[i],
          yPointList[i]
        )
      ) {
        cPointList[i] = 1
        xAverage += xPointList[i]
        yAverage += yPointList[i]
        averageCount++
      } else {
        cPointList[i] = -1
      }
    }

xAverage /= averageCount
    yAverage /= averageCount

xAverageElement.innerHTML = 'x average: ' + xAverage
    yAverageElement.innerHTML = 'y average:' + yAverage

pointPlot.data.update()
  }
})