Applies to: Nevron Chart for .NET
How how to apply a range of colors to a line series?
This article discusses how to apply a range of colors to a line series.
It is a common requirement to plot a line where certain ranges of values are color coded. This improves the visual impact and makes the chart more readable.
The following code shows how to apply two color zones to a line series:
[C#]
private void Form1_Load(object sender, EventArgs e)
{
NCartesianChart chart = (NCartesianChart)nChartControl1.Charts[0];
NLineSeries line = new NLineSeries();
line.UseXValues = true;
line.DataLabelStyle.Visible = false;
chart.Series.Add(line);
for (int i = 0; i < 100; i++)
{
line.Values.Add(Math.Cos(i * 180.0 / Math.PI) * 50);
line.XValues.Add(i);
}
ApplyLineColorRanges(new NRange1DD[] { new NRange1DD(-50, -20), new NRange1DD(20, 50) },
new Color[] { Color.Blue, Color.Red }, line);
}
///
/// </summary>
/// <param name="ranges"></param>
/// <param name="colors"></param>
/// <param name="line"></param>
private static void ApplyLineColorRanges(NRange1DD[] ranges, Color[] colors, NLineSeries line)
{
Color defaultColor = line.BorderStyle.Color;
NLength width = line.BorderStyle.Width;
// pass 1 split all lines that are intersected by range
for (int i = 0; i < ranges.Length; i++)
{
NRange1DD range = ranges[i];
SplitLineAtY(range.Begin, line);
SplitLineAtY(range.End, line);
}
for (int i = 0; i < ranges.Length; i++)
{
ApplyColorRange(width, colors[i], ranges[i], line);
}
}
/// <summary>
/// Splits the line at the specified y cooridnate.
/// </summary>
/// <param name="y"></param>
/// <param name="line"></param>
private static void SplitLineAtY(double y, NLineSeries line)
{
int count = line.Values.Count;
for (int i = 1; i < count; i++)
{
double y1 = (double)line.Values[i - 1];
double y2 = (double)line.Values[i];
if (y1 == y2)
continue;
if (y1 < y2)
{
// ascending
if (y1 >= y)
continue;
if (y2 <= y)
continue;
}
else
{
// descending
if (y2 >= y)
continue;
if (y1 <= y)
continue;
}
// split
double x1 = (double)line.XValues[i - 1];
double x2 = (double)line.XValues[i];
double dy = y2 - y1;
double dx = x2 - x1;
double x3 = x1 + dx * (y - y1) / dy;
line.XValues.Insert(i, x3);
line.Values.Insert(i, y);
i++;
count++;
}
}
/// <summary>
/// Applies the specified color to the range
/// </summary>
/// <param name="width"></param>
/// <param name="color"></param>
/// <param name="range"></param>
/// <param name="line"></param>
private static void ApplyColorRange(NLength width, Color color, NRange1DD range, NLineSeries line)
{
int count = line.Values.Count - 1;
for (int i = 0; i < count; i++)
{
double y1 = (double)line.Values[i];
double y2 = (double)line.Values[i + 1];
if (range.Contains(y1, 0.0001) && range.Contains(y2, 0.0001))
{
line.BorderStyles[i] = new NStrokeStyle(width, color);
}
}
}
[VB.NET]
Private Sub Form1_Load(sender As Object, e As EventArgs)
Dim chart As NCartesianChart = DirectCast(nChartControl1.Charts(0), NCartesianChart)
Dim line As New NLineSeries()
line.UseXValues = True
line.DataLabelStyle.Visible = False
chart.Series.Add(line)
For i As Integer = 0 To 99
line.Values.Add(Math.Cos(i * 180.0 / Math.PI) * 50)
line.XValues.Add(i)
Next
ApplyLineColorRanges(New NRange1DD() {New NRange1DD(-50, -20), New NRange1DD(20, 50)}, New Color() {Color.Blue, Color.Red}, line)
End Sub
'''
''' </summary>
''' <param name="ranges"></param>
''' <param name="colors"></param>
''' <param name="line"></param>
Private Shared Sub ApplyLineColorRanges(ranges As NRange1DD(), colors As Color(), line As NLineSeries)
Dim defaultColor As Color = line.BorderStyle.Color
Dim width As NLength = line.BorderStyle.Width
' pass 1 split all lines that are intersected by range
For i As Integer = 0 To ranges.Length - 1
Dim range As NRange1DD = ranges(i)
SplitLineAtY(range.Begin, line)
SplitLineAtY(range.[End], line)
Next
For i As Integer = 0 To ranges.Length - 1
ApplyColorRange(width, colors(i), ranges(i), line)
Next
End Sub
''' <summary>
''' Splits the line at the specified y cooridnate.
''' </summary>
''' <param name="y"></param>
''' <param name="line"></param>
Private Shared Sub SplitLineAtY(y As Double, line As NLineSeries)
Dim count As Integer = line.Values.Count
For i As Integer = 1 To count - 1
Dim y1 As Double = CDbl(line.Values(i - 1))
Dim y2 As Double = CDbl(line.Values(i))
If y1 = y2 Then
Continue For
End If
If y1 < y2 Then
' ascending
If y1 >= y Then
Continue For
End If
If y2 <= y Then
Continue For
End If
Else
' descending
If y2 >= y Then
Continue For
End If
If y1 <= y Then
Continue For
End If
End If
' split
Dim x1 As Double = CDbl(line.XValues(i - 1))
Dim x2 As Double = CDbl(line.XValues(i))
Dim dy As Double = y2 - y1
Dim dx As Double = x2 - x1
Dim x3 As Double = x1 + dx * (y - y1) / dy
line.XValues.Insert(i, x3)
line.Values.Insert(i, y)
i += 1
count += 1
Next
End Sub
''' <summary>
''' Applies the specified color to the range
''' </summary>
''' <param name="width"></param>
''' <param name="color"></param>
''' <param name="range"></param>
''' <param name="line"></param>
Private Shared Sub ApplyColorRange(width As NLength, color As Color, range As NRange1DD, line As NLineSeries)
Dim count As Integer = line.Values.Count - 1
For i As Integer = 0 To count - 1
Dim y1 As Double = CDbl(line.Values(i))
Dim y2 As Double = CDbl(line.Values(i + 1))
If range.Contains(y1, 0.0001) AndAlso range.Contains(y2, 0.0001) Then
line.BorderStyles(i) = New NStrokeStyle(width, color)
End If
Next
End Sub
Article ID: 237, Created On: 11/26/2013, Modified: 11/26/2013