Simple Bar Charts

It is common to use charts to display a series of simple values, like product prices. This type of chart is useful because it shows the relative magnitude of each value in a quick and effective way.

The main characteristic of this type of chart is that each point conveys only one piece of information. When creating these charts, the value being displayed is assigned to the Y values of the series. The X values only provide constant spacing between the points, and usually display labels attached to each data point.

The recommended chart types for this type of information are Bar and Pie charts.

The following illustration shows a simple bar chart with product prices (Beverages from the NorthWind product list).

Note that the bars are displayed horizontally, in order to provide room for the product names along the vertical axis. This is done using the ChartArea.Inverted property.

The following code creates the bar chart in the preceding graphic. In actual applications, the code would be even simpler because some properties would be set at design time.

· Visual Basic

' get chart data

Dim data As DataView = _dataSet.Tables("Products").DefaultView

data.Sort = "UnitPrice"

data.RowFilter = "CategoryID = 1" ' beverages

' configure the chart

C1Chart1.Reset()

C1Chart1.ChartArea.Inverted = true

C1Chart1.ChartGroups(0).ChartType = Chart2DTypeEnum.Bar

' create single series for product price

Dim dscoll As ChartDataSeriesCollection = C1Chart1.ChartGroups(0).ChartData.SeriesList

dscoll.Clear()

Dim series As ChartDataSeries = dscoll.AddNewSeries()

series.Label = "Product Prices"

' populate the series

series.PointData.Length = data.Count

Dim i As Integer

For i = 0 To data.Count – 1

series.X(i) = I

series.Y(i) = data(i)("UnitPrice")

Next I

' attach product names to x-axis

Dim ax As Axis = C1Chart1.ChartArea.AxisX

ax.AnnoMethod = AnnotationMethodEnum.ValueLabels

For i = 0 To data.Count – 1

ax.ValueLabels.Add(i, CType(data(i)("ProductName"), String))

Next I

' configure y-axis

Dim ay As Axis = C1Chart1.ChartArea.AxisY

ay.AnnoFormat = FormatEnum.NumericCurrency

· C#

// get chart data

DataView data = _dataSet.Tables["Products"].DefaultView;

data.Sort = "UnitPrice";

data.RowFilter = "CategoryID = 1"; // beverages

// configure the chart

C1Chart1.Reset();

C1Chart1.ChartArea.Inverted = true;

C1Chart1.ChartGroups[0].ChartType = Chart2DTypeEnum.Bar;

// create single series for product price

ChartDataSeriesCollection dscoll = C1Chart1.ChartGroups[0].ChartData.SeriesList;

dscoll.Clear();

ChartDataSeries series = dscoll.AddNewSeries();

series.Label = "Product Prices";

// populate the series

series.PointData.Length = data.Count;

for (int i = 0; i < data.Count; i++)

{

series.X[i] = i;

series.Y[i] = data[i]["UnitPrice"];

}

// attach product names to x-axis

Axis ax = C1Chart1.ChartArea.AxisX;

ax.AnnoMethod = AnnotationMethodEnum.ValueLabels;

for (int i = 0; i < data.Count; i++)

ax.ValueLabels.Add(i, (string)data[i]["ProductName"]);

// configure y-axis

Axis ay = C1Chart1.ChartArea.AxisY;

ay.AnnoFormat = FormatEnum.NumericCurrency;

· Delphi

var

data: DataView;

dscoll: ChartDataSeriesCollection;

series: ChartDataSeries;

i: Integer;

ax, ay: Axis;

begin

// get chart data

data := _dataSet.Tables['Products'].DefaultView;

data.Sort := 'UnitPrice';

data.RowFilter := 'CategoryID = 1'; // beverages

// configure the chart

C1Chart1.Reset();

C1Chart1.ChartArea.Inverted := true;

C1Chart1.ChartGroups[0].ChartType := Chart2DTypeEnum.Bar;

// create single series for product price

dscoll = C1Chart1.ChartGroups[0].ChartData.SeriesList;

dscoll.Clear();

series := dscoll.AddNewSeries();

series.Label := 'Product Prices';

// populate the series

series.PointData.Length := data.Count;

for i := 0 to data.Count – 1 do

begin

series.X[i] := i;

series.Y[i] := data[i]['UnitPrice'];

end;

// attach product names to x-axis

ax := C1Chart1.ChartArea.AxisX;

ax.AnnoMethod := AnnotationMethodEnum.ValueLabels;

for i := 0 to data.Count – 1

ax.ValueLabels.Add(i, String(data[i]['ProductName']));

// configure y-axis

ay := C1Chart1.ChartArea.AxisY;

ay.AnnoFormat := FormatEnum.NumericCurrency;

end;

It is common to show more than one data series on a chart, and that is easy to do with C1Chart. The code would look similar to the above, except you would add additional lists to the ChartDataSeriesCollection.