Merge pull request #168 from kunalverma25/BarChartsNegativeValueFix

Negative Value Visualisation fix for Bar/Grouped/Horizontal Bar Charts

Sources/SwiftUICharts/BarChart/Models/ChartData/BarChartData.swift

@@ -1,6 +1,6 @@
 //
 //  BarChartData.swift
-//  
+//
 //
 //  Created by Will Dale on 23/01/2021.
 //
@@ -41,7 +41,7 @@ public final class BarChartData: CTBarChartDataProtocol, GetDataProtocol, Publis
     ///   - dataSets: Data to draw and style the bars.
     ///   - metadata: Data model containing the charts Title, Subtitle and the Title for Legend.
     ///   - xAxisLabels: Labels for the X axis instead of the labels in the data points.
-    ///   - yAxisLabels: Labels for the Y axis instead of the labels generated from data point values.   
+    ///   - yAxisLabels: Labels for the Y axis instead of the labels generated from data point values.
     ///   - barStyle: Control for the aesthetic of the bar chart.
     ///   - chartStyle: The style data for the aesthetic of the chart.
     ///   - noDataText: Customisable Text to display when where is not enough data to draw the chart.
@@ -148,11 +148,17 @@ public final class BarChartData: CTBarChartDataProtocol, GetDataProtocol, Publis
 
     public final func getPointLocation(dataSet: BarDataSet, touchLocation: CGPoint, chartSize: CGRect) -> CGPoint? {
         let xSection: CGFloat = chartSize.width / CGFloat(dataSet.dataPoints.count)
-        let ySection: CGFloat = chartSize.height / CGFloat(self.maxValue)
+        var ySection: CGFloat = chartSize.height / CGFloat(self.maxValue)
         let index: Int = Int((touchLocation.x) / xSection)
         if index >= 0 && index < dataSet.dataPoints.count {
-            return CGPoint(x: (CGFloat(index) * xSection) + (xSection / 2),
-                           y: (chartSize.size.height - CGFloat(dataSet.dataPoints[index].value) * ySection))
+            let x = (CGFloat(index) * xSection) + (xSection / 2)
+            var y = (chartSize.size.height - CGFloat(dataSet.dataPoints[index].value) * ySection)
+            if self.minValue.isLess(than: 0) {
+                ySection = chartSize.height / (CGFloat(self.maxValue) - CGFloat(self.minValue))
+                y = (chartSize.size.height - (CGFloat(dataSet.dataPoints[index].value) * ySection) + (CGFloat(self.minValue) * ySection))
+            }
+            return CGPoint(x: x,
+                           y: y)
         }
         return nil
     }

Sources/SwiftUICharts/BarChart/Models/ChartData/GroupedBarChartData.swift

@@ -1,6 +1,6 @@
 //
 //  MultiBarChartData.swift
-//  
+//
 //
 //  Created by Will Dale on 26/01/2021.
 //
@@ -49,7 +49,7 @@ public final class GroupedBarChartData: CTMultiBarChartDataProtocol, GetDataProt
     ///   - groups: Information for how to group the data points.
     ///   - metadata: Data model containing the charts Title, Subtitle and the Title for Legend.
     ///   - xAxisLabels: Labels for the X axis instead of the labels in the data points.
-    ///   - yAxisLabels: Labels for the Y axis instead of the labels generated from data point values.   
+    ///   - yAxisLabels: Labels for the Y axis instead of the labels generated from data point values.
     ///   - barStyle: Control for the aesthetic of the bar chart.
     ///   - chartStyle: The style data for the aesthetic of the chart.
     ///   - noDataText: Customisable Text to display when where is not enough data to draw the chart.
@@ -185,7 +185,7 @@ public final class GroupedBarChartData: CTMultiBarChartDataProtocol, GetDataProt
 
         // Make those sections take account of spacing between groups.
         let xSection: CGFloat = superXSection - compensation
-        let ySection: CGFloat = chartSize.height / CGFloat(self.maxValue)
+        var ySection: CGFloat = chartSize.height / CGFloat(self.maxValue)
 
         let index: Int = Int((touchLocation.x - CGFloat(groupSpacing * CGFloat(superIndex))) / xSection)
 
@@ -197,8 +197,14 @@ public final class GroupedBarChartData: CTMultiBarChartDataProtocol, GetDataProt
                 let element: CGFloat = (CGFloat(subIndex) * xSubSection) + (xSubSection / 2)
                 let section: CGFloat = (superXSection * CGFloat(superIndex))
                 let spacing: CGFloat = ((groupSpacing / CGFloat(dataSets.dataSets.count)) * CGFloat(superIndex))
-                return CGPoint(x: element + section + spacing,
-                               y: (chartSize.height - CGFloat(subDataSet.dataPoints[subIndex].value) * ySection))
+                let x = element + section + spacing
+                var y = (chartSize.height - CGFloat(subDataSet.dataPoints[subIndex].value) * ySection)
+                if self.minValue.isLess(than: 0) {
+                    ySection = chartSize.height / (CGFloat(self.maxValue) - CGFloat(self.minValue))
+                    y = (chartSize.height - (CGFloat(subDataSet.dataPoints[subIndex].value) * ySection) + (CGFloat(self.minValue) * ySection))
+                }
+                return CGPoint(x: x,
+                               y: y)
             }
         }
         return nil

Sources/SwiftUICharts/BarChart/Models/ChartData/HorizontalBarChartData.swift

@@ -1,6 +1,6 @@
 //
 //  HorizontalBarChartData.swift
-//  
+//
 //
 //  Created by Will Dale on 26/04/2021.
 //
@@ -120,10 +120,6 @@ public final class HorizontalBarChartData: CTHorizontalBarChartDataProtocol, Get
                         Spacer()
                             .frame(minHeight: 0, maxHeight: 500)
                     }
-                    if self.chartStyle.xAxisLabelPosition == .bottom {
-                        Spacer()
-                            .frame(height: yAxisPaddingHeight + 8) // Why 8 ?
-                    }
                 }
 
             case .chartData:
@@ -187,11 +183,17 @@ public final class HorizontalBarChartData: CTHorizontalBarChartDataProtocol, Get
 
     public final func getPointLocation(dataSet: BarDataSet, touchLocation: CGPoint, chartSize: CGRect) -> CGPoint? {
         let ySection: CGFloat = chartSize.height / CGFloat(dataSet.dataPoints.count)
-        let xSection: CGFloat = chartSize.width / CGFloat(self.maxValue)
+        var xSection: CGFloat = chartSize.width / CGFloat(self.maxValue)
         let index: Int = Int((touchLocation.y) / ySection)
         if index >= 0 && index < dataSet.dataPoints.count {
-            return CGPoint(x: (CGFloat(dataSet.dataPoints[index].value) * xSection),
-                           y: (CGFloat(index) * ySection) + (ySection / 2))
+            var x = (CGFloat(dataSet.dataPoints[index].value) * xSection)
+            let y = (CGFloat(index) * ySection) + (ySection / 2)
+            if self.minValue.isLess(than: 0) {
+                xSection = chartSize.width / (CGFloat(self.maxValue) - CGFloat(self.minValue))
+                x = (CGFloat(dataSet.dataPoints[index].value) * xSection) - (CGFloat(self.minValue) * xSection)
+            }
+            return CGPoint(x: x,
+                           y: y)
         }
         return nil
     }

Sources/SwiftUICharts/BarChart/Views/BarChart.swift

@@ -1,6 +1,6 @@
 //
 //  BarChart.swift
-//  
+//
 //
 //  Created by Will Dale on 11/01/2021.
 //
@@ -71,5 +71,8 @@ public struct BarChart<ChartData>: View where ChartData: BarChartData {
                 }
             } else { CustomNoDataView(chartData: chartData) }
         }
+        .if(chartData.minValue.isLess(than: 0)) {
+            $0.scaleEffect(y: CGFloat(chartData.maxValue/(chartData.maxValue - chartData.minValue)), anchor: .top)
+        }
     }
 }

Sources/SwiftUICharts/BarChart/Views/GroupedBarChart.swift

@@ -1,6 +1,6 @@
 //
 //  GroupedBarChart.swift
-//  
+//
 //
 //  Created by Will Dale on 25/01/2021.
 //
@@ -73,6 +73,9 @@ public struct GroupedBarChart<ChartData>: View where ChartData: GroupedBarChartD
                 }
             } else { CustomNoDataView(chartData: chartData) }
         }
+        .if(chartData.minValue.isLess(than: 0)) {
+            $0.scaleEffect(y: CGFloat(chartData.maxValue/(chartData.maxValue - chartData.minValue)), anchor: .top)
+        }
     }
 }
 

Sources/SwiftUICharts/BarChart/Views/HorizontalBarChart.swift

@@ -1,6 +1,6 @@
 //
 //  HorizontalBarChart.swift
-//  
+//
 //
 //  Created by Will Dale on 26/04/2021.
 //
@@ -29,13 +29,15 @@ public struct HorizontalBarChart<ChartData>: View where ChartData: HorizontalBar
                         HorizontalBarChartDataPointSubView(chartData: chartData)
                             .accessibilityLabel(LocalizedStringKey(chartData.metadata.title))
                     }
-
                 }
                 // Needed for axes label frames
                 .onChange(of: geo.frame(in: .local)) { value in
                     self.chartData.viewData.chartSize = value
                 }
             } else { CustomNoDataView(chartData: chartData) }
         }
+        .if(chartData.minValue.isLess(than: 0)) {
+            $0.scaleEffect(x: CGFloat(chartData.maxValue/(chartData.maxValue - chartData.minValue)), anchor: .trailing)
+        }
     }
 }