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Merge pull request #45 from algrid/fix-43
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Custom threshold for positive/negative data display
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@gpbl
gpbl authored Nov 14, 2016
2 parents 0ea27f7 + 1f8cd25 commit 717c660
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Showing 2 changed files with 24 additions and 31 deletions.
51 changes: 22 additions & 29 deletions Source/Chart.swift
View file
Original file line number Diff line number Diff line change
Expand Up @@ -283,7 +283,7 @@ open class Chart: UIControl {
for (index, series) in self.series.enumerated() {

// Separate each line in multiple segments over and below the x axis
let segments = Chart.segmentLine(series.data as ChartLineSegment)
let segments = Chart.segmentLine(series.data as ChartLineSegment, zeroLevel: series.colors.zeroLevel)

segments.forEach({ segment in
let scaledXValues = scaleValuesOnXAxis( segment.map({ return $0.x }) )
Expand Down Expand Up @@ -405,30 +405,20 @@ open class Chart: UIControl {
return scaled
}

fileprivate func getZeroValueOnYAxis() -> Float {
if min.y > 0 {
fileprivate func getZeroValueOnYAxis(zeroLevel: Float) -> Float {
if min.y > zeroLevel {
return scaleValueOnYAxis(min.y)
} else {
return scaleValueOnYAxis(0)
return scaleValueOnYAxis(zeroLevel)
}

}

// MARK: - Drawings

fileprivate func isVerticalSegmentAboveXAxis(_ yValues: Array<Float>) -> Bool {

// YValues are "reverted" from top to bottom, so min is actually the maxz
let min = yValues.max()!
let zero = getZeroValueOnYAxis()

return min <= zero

}

fileprivate func drawLine(_ xValues: Array<Float>, yValues: Array<Float>, seriesIndex: Int) {

let isAboveXAxis = isVerticalSegmentAboveXAxis(yValues)
// YValues are "reverted" from top to bottom, so 'above' means <= level
let isAboveZeroLine = yValues.max()! <= self.scaleValueOnYAxis(series[seriesIndex].colors.zeroLevel)
let path = CGMutablePath()
path.move(to: CGPoint(x: CGFloat(xValues.first!), y: CGFloat(yValues.first!)))
for i in 1..<yValues.count {
Expand All @@ -440,7 +430,7 @@ open class Chart: UIControl {
lineLayer.frame = self.bounds
lineLayer.path = path

if isAboveXAxis {
if isAboveZeroLine {
lineLayer.strokeColor = series[seriesIndex].colors.above.cgColor
} else {
lineLayer.strokeColor = series[seriesIndex].colors.below.cgColor
Expand All @@ -455,9 +445,10 @@ open class Chart: UIControl {
}

fileprivate func drawArea(_ xValues: Array<Float>, yValues: Array<Float>, seriesIndex: Int) {
let isAboveXAxis = isVerticalSegmentAboveXAxis(yValues)
// YValues are "reverted" from top to bottom, so 'above' means <= level
let isAboveZeroLine = yValues.max()! <= self.scaleValueOnYAxis(series[seriesIndex].colors.zeroLevel)
let area = CGMutablePath()
let zero = CGFloat(getZeroValueOnYAxis())
let zero = CGFloat(getZeroValueOnYAxis(zeroLevel: series[seriesIndex].colors.zeroLevel))

area.move(to: CGPoint(x: CGFloat(xValues[0]), y: zero))
for i in 0..<xValues.count {
Expand All @@ -468,7 +459,7 @@ open class Chart: UIControl {
areaLayer.frame = self.bounds
areaLayer.path = area
areaLayer.strokeColor = nil
if isAboveXAxis {
if isAboveZeroLine {
areaLayer.fillColor = series[seriesIndex].colors.above.withAlphaComponent(areaAlphaComponent).cgColor
} else {
areaLayer.fillColor = series[seriesIndex].colors.below.withAlphaComponent(areaAlphaComponent).cgColor
Expand Down Expand Up @@ -498,7 +489,7 @@ open class Chart: UIControl {

// horizontal axis when y = 0
if min.y < 0 && max.y > 0 {
let y = CGFloat(getZeroValueOnYAxis())
let y = CGFloat(getZeroValueOnYAxis(zeroLevel: 0))
context.move(to: CGPoint(x: CGFloat(0), y: y))
context.addLine(to: CGPoint(x: CGFloat(drawingWidth), y: y))
context.strokePath()
Expand Down Expand Up @@ -597,7 +588,7 @@ open class Chart: UIControl {

let scaled = scaleValuesOnYAxis(labels)
let padding: CGFloat = 5
let zero = CGFloat(getZeroValueOnYAxis())
let zero = CGFloat(getZeroValueOnYAxis(zeroLevel: 0))

scaled.enumerated().forEach { (i, value) in

Expand Down Expand Up @@ -755,7 +746,7 @@ open class Chart: UIControl {
Segment a line in multiple lines when the line touches the x-axis, i.e. separating
positive from negative values.
*/
fileprivate class func segmentLine(_ line: ChartLineSegment) -> Array<ChartLineSegment> {
fileprivate class func segmentLine(_ line: ChartLineSegment, zeroLevel: Float) -> Array<ChartLineSegment> {
var segments: Array<ChartLineSegment> = []
var segment: ChartLineSegment = []

Expand All @@ -764,9 +755,9 @@ open class Chart: UIControl {
segment.append(point)
if i < line.count - 1 {
let nextPoint = line[i+1]
if point.y * nextPoint.y <= 0 || point.y <= 0 && nextPoint.y == 0 {
// The sign changed, close the segment with the intersection on x-axis
let closingPoint = Chart.intersectionOnXAxisBetween(point, and: nextPoint)
if point.y >= zeroLevel && nextPoint.y < zeroLevel || point.y < zeroLevel && nextPoint.y >= zeroLevel {
// The segment intersects zeroLevel, close the segment with the intersection point
let closingPoint = Chart.intersectionWithLevel(point, and: nextPoint, level: zeroLevel)
segment.append(closingPoint)
segments.append(segment)
// Start a new segment
Expand All @@ -782,9 +773,11 @@ open class Chart: UIControl {
}

/**
Return the intersection of a line between two points on the x-axis
Return the intersection of a line between two points and 'y = level' line
*/
fileprivate class func intersectionOnXAxisBetween(_ p1: ChartPoint, and p2: ChartPoint) -> ChartPoint {
return (x: p1.x - (p2.x - p1.x) / (p2.y - p1.y) * p1.y, y: 0)
fileprivate class func intersectionWithLevel(_ p1: ChartPoint, and p2: ChartPoint, level: Float) -> ChartPoint {
let dy1 = level - p1.y
let dy2 = level - p2.y
return (x: (p2.x * dy1 - p1.x * dy2) / (dy1 - dy2), y: level)
}
}
4 changes: 2 additions & 2 deletions Source/ChartSeries.swift
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,10 +16,10 @@ open class ChartSeries {
open var line: Bool = true
open var color: UIColor = ChartColors.blueColor() {
didSet {
colors = (above: color, below: color)
colors = (above: color, below: color, 0)
}
}
var colors: (above: UIColor, below: UIColor) = (above: ChartColors.blueColor(), below: ChartColors.redColor())
open var colors: (above: UIColor, below: UIColor, zeroLevel: Float) = (above: ChartColors.blueColor(), below: ChartColors.redColor(), 0)

public init(_ data: Array<Float>) {
self.data = []
Expand Down

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