com.barrybecker4.ui.renderers.model.HistogramModel.scala Maven / Gradle / Ivy
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// Copyright by Barry G. Becker, 2018. Licensed under MIT License: http://www.opensource.org/licenses/MIT
package com.barrybecker4.ui.renderers.model
import com.barrybecker4.math.function.InvertibleFunction
/**
* Manages the statistics for a histogram.
* The histogram this represent can be incrementally modified.
* @param data the initial histogram data
* @param xFunction manner in which the x domain is mapped. For example it can be linear or log scale.
* @param integralXValues if true, then the x values will assumed to be only equal to the low bin cutPoint value.
* This implies that the the median only be one of those low bin cutPoint values.
*/
class HistogramModel(val data: Array[Int],
val xFunction: InvertibleFunction,
val integralXValues: Boolean = false) {
assert(!data.exists(_ < 0), "Histograms can only have non-negative values")
var sum: Double = data.sum
var mean: Double = calcMean()
def numBars: Int = this.data.length
def getValueForPosition(pos: Int): Double = xFunction.getInverseValue(pos)
def getPositionForValue(value: Double): Int = xFunction.getValue(value).toInt
def getMaxHeight: Int = Math.max(1, data.max)
// Used only by unit test
def calcMedian(medianPos: Int): Double = {
val m = getValueForPosition(medianPos)
if (integralXValues) m
else {
val rightVal = if (medianPos >= numBars) xFunction.getDomain.max else getValueForPosition(medianPos + 1)
(m + rightVal) / 2.0
}
}
/**
* @param xValue add some data to the histogram. This will change bar height representing count for specified value.
*/
def increment(xValue: Double): Unit = {
val xPos = xFunction.getValue(xValue).toInt
// it has to be in range to be shown in the histogram.
if (xPos >= 0 && xPos < data.length) data(xPos) += 1
mean = (sum * mean + xValue) / (sum + 1)
sum += 1
}
def calcMean(): Double = {
var sumXValues: Double = 0
for (i <- data.indices) {
// the bin holds all values between xInverse(i) and xInverse(i + 1)
val lowInverse = xFunction.getInverseValue(i)
val binAvgX =
if (integralXValues) lowInverse
else (lowInverse + xFunction.getInverseValue(i + 1)) / 2.0
sumXValues += data(i) * binAvgX
}
if (sum == 0) 0 else sumXValues / sum
}
def calcMedianPos: Int = {
val halfTotal: Double = sum / 2.0
var medianPos = 0
var cumulativeTotal = 0
while (cumulativeTotal < halfTotal && medianPos < data.length) {
cumulativeTotal += data(medianPos)
medianPos += 1
}
if (medianPos == data.length && cumulativeTotal < halfTotal)
println(s"Warning: medianPosition: $medianPos too big and will not be shown. " +
s"cumTotal = $cumulativeTotal halfTotal = $halfTotal")
if (medianPos > 0 && data(medianPos - 1) > 0)
medianPos -= ((cumulativeTotal - halfTotal) / data(medianPos - 1)).toInt
medianPos - 1
}
}