Chart displaying "Trendline Error"

Create Excel charts with trendline, error bars, data tables, data labels in C# using Spire.XLS

Tools free us from extra work. Here I use .dll from free Spire.XLS to create Excel charts and add all the chart tools I mentioned above if you would like to try, you could get it from E-iceblue official website or Nuget.

Step 1: I use the following code to create a column clustered chart (see the screenshot) with trendline and data table using the .dll in Visual Studio.

Screenshot: (R2=0.9688, which means the trendline is very fit to the data.)


Figure 4: Chart

Code
//Create an Excel and add a sheet
Workbook workbook = new Workbook();
workbook.CreateEmptySheets(1);
Worksheet sheet = workbook.Worksheets[0];

//Fill Excel cells with sample data
sheet.Name = "sample 1";
sheet.Range["A1"].Value = "Month";
sheet.Range["A2"].Value = "Jan.";
sheet.Range["A3"].Value = "Feb.";
sheet.Range["A4"].Value = "Mar.";
sheet.Range["A5"].Value = "Apr.";
sheet.Range["A6"].Value = "May.";
sheet.Range["A7"].Value = "Jun.";
sheet.Range["B1"].Value = "Porter";
sheet.Range["B2"].NumberValue = 15;
sheet.Range["B3"].NumberValue = 18;
sheet.Range["B4"].NumberValue = 24;
sheet.Range["B5"].NumberValue = 32;
sheet.Range["B6"].NumberValue = 37;
sheet.Range["B7"].NumberValue = 40;
sheet.Range["C1"].Value = "Harry";
sheet.Range["C2"].NumberValue = 38;
sheet.Range["C3"].NumberValue = 32;
sheet.Range["C4"].NumberValue = 17;
sheet.Range["C5"].NumberValue = 35;
sheet.Range["C6"].NumberValue = 45;
sheet.Range["C7"].NumberValue = 43;
sheet.Range["D1"].Value = "Chocolate";
sheet.Range["D2"].NumberValue = 30;
sheet.Range["D3"].NumberValue = 28;
sheet.Range["D4"].NumberValue = 35;
sheet.Range["D5"].NumberValue = 23;
sheet.Range["D6"].NumberValue = 33;
sheet.Range["D7"].NumberValue = 38;

//Create a columnclustered chart
Chart chart = sheet.Charts.Add(ExcelChartType.ColumnClustered);
chart.DataRange = sheet.Range["B1:D7"];
chart.SeriesDataFromRange = false;
chart.TopRow = 4;
chart.BottomRow = 27;
chart.LeftColumn = 2;
chart.RightColumn =11;
chart.ChartTitle = "Chart with trendline and datatable";
chart.ChartTitleArea.IsBold = true;
chart.ChartTitleArea.Size = 12;
Spire.Xls.Charts.ChartSerie cs1 = chart.Series[0];
cs1.CategoryLabels = sheet.Range["A2:A7"];

//Add trendline and datatable to the chart
chart.Series[0].TrendLines.Add(TrendLineType.Exponential);
chart.HasDataTable = true;

//Save the document as .xlsx file
workbook.SaveToFile("Sample1.xlsx", ExcelVersion.Version2010);
Step 2: Using the same sample data, I create another chart to show the error bars in Excel using C#. Only the different codes are listed.
Chart chart = sheet.Charts.Add(ExcelChartType.Line);
chart.DataRange = sheet.Range["C1:D7"];
chart.SeriesDataFromRange = false;
chart.TopRow = 4;
chart.BottomRow = 27;
chart.LeftColumn = 2;
chart.RightColumn =11;
chart.ChartTitle = "Chart with error bars";
chart.ChartTitleArea.IsBold = true;
chart.ChartTitleArea.Size = 12;
chart.Series[0].CategoryLabels = sheet.Range["A2:A7"];
chart.Series[0].ErrorBar(true, ErrorBarIncludeType.Plus, ErrorBarType.Fixed, 2);
chart.Series[1].ErrorBar(true, ErrorBarIncludeType.Both, ErrorBarType.Percentage,5);