QCChart2D CF Charting Tools for .Net CF FAQs

Frequently Asked Questions QCChart2D CF

FAQs

Is the QCChart2D CF for the .Net Compact Framework software compatible with the QCChart2D for .Net software?
Why doesn’t your QCChart2D CF software appear on the .Net Compact Framework toolbox. And why can’t I add it there.
How do you create a chart with multiple coordinate systems and axes?
Can I add new axes, text objects, plot objects, and images to a chart after it is already displayed; or must I create a new chart from scratch taking into account the additional objects?
How do you zoom charts that use multiple coordinate systems?
How do you handle missing data points in a chart?
How do you update a chart in real-time?
How do I prevent flicker when updating my charts on real-time?
How do you implement drill down, or data tool tips in a chart?
I do not want to my graph to auto-scale. How do I setup the graph axes for a specific range?
How do I update my data, and auto-rescale the chart scales and axes to reflect the new data, after it has already been drawn?
When I use the auto-scale and auto-axis routines my semi-log chart has the logarithmic axis scaled using powers of 10 (1, 10,100, 1000, etc.) as the starting and ending values, or as the major tick interval for labeling. How do I make my log graphs start at 20 and end at 50,000, with major tick marks at 20, 200, 2000 and 20000?
How do I create and use custom, multi-line string labels as the axis labels for my graph?
How do I place more than one graph in a view?
How do I use the QCChart2D CF software to generate JPG, DIB, BMP, GIF, EMF, WMF, etc. files?
Sometimes the major tick marks of an axis are missing the associated tick mark label ?
How do I change the order the chart objects are drawn? For example, I want one of my grid objects to be drawn under the charts line plot objects, and another grid object to be drawn top of the charts line plot objects.
How to I use a Forms scrollbar object to control horizontal scrolling of the data in my chart?
I am trying to plot 100,000 data points and it takes too long to draw the graph. What is wrong with the software and what can I do to make it faster?
How do I get data from my database into a chart?
Are you going to add additional real-time routines to the QCChart2D CF for the .Net Compact Framework library?
Are you going to add 3D routines to the QCChart2D CF for the .Net Compact Framework library?

1. Is source code written for the the QCChart2D CF for the .Net Compact Framework software compatible with the QCChart2D for .Net software?

Yes, assuming you do not use any of the features that are not supported in QCChart2D CF, such as line styles, pen width greater than one, rotated text, printer output and output of image files.

2. Why doesn’t your QCChart2D CF software appear on the .Net Compact Framework toolbox. And why can’t I add it there.

The .Net Compact Framework toolbox is for form based design. The weakness of form based design is that it does not take into account different screen resolutions and aspect ratios. A form based display that works under portrait mode will be cut-off when viewed under the new landscape modes supported by the latest .Net Compact Framework devices. Design for the Windows CE emulator display that ships with VS 2003 and your form will not fit on the smaller 240x240 display of Pocket PC phones. The only solution for form based design is to identify the size and position of every control on the form, and recalculate the size and position based on the x and y resolution of the screen. Unfortunately, that completely eliminates any productivity gains associated with form based design. Instead of tool box support we provide simple constructors for placing a ChartView in a parent form using a simple positioning rectangle, that you can easily adjust at runtime to match the x and y screen resolution of the display. Our intelligent font re-scaling enable you to design at one screen resolution and display at another.

You can’t add it to the toolbox (or if you do it is grayed out) because the .Net CF toolbox requires that you supply a unique version of the control, compiled using different runtime libraries than the regular version of the control and that works only works explicitly with the toolbox, and we do not do that.

3. How do you create a chart with multiple coordinate systems and axes?

A chart can have as many coordinate systems and axes as you want. A single coordinate system can have one or more x- and/or y-axes. The most common use for multiple axes in a single coordinate system is to place y-axes on both the left and the right sides of a chart, and x-axes above and below. The left and bottom axes usually have numeric or date labels, and the top and right axes just tick marks. This does not have to be the case though; every axis can have axis labels if you want. In general, the axis position in the chart is determined by its intercept. The default value of the intercept is set to the minimums of the coordinate system that the axis is placed in. Adjusting the intercept using the SetAxisIntercept method changes the position of the axis in the chart. The axis intercept value is set using units of the coordinate system at right angles to the axis. The example below, extracted from the LineFill example, places y-axes on both the left and right of the chart.

[C#]

TimeAxis xAxis = new TimeAxis(pTransform1);

chartVu.AddChartObject(xAxis);

TimeAxis xAxis = new TimeAxis(pTransform1);

xAxis.SetColor(Color.White);

chartVu.AddChartObject(xAxis);

LinearAxis yAxis = new LinearAxis(pTransform1, ChartObj.Y_AXIS);

// Default places y-axis at miniumum of x-coordinate scale

yAxis.SetColor(Color.White);

chartVu.AddChartObject(yAxis);

LinearAxis yAxis2 = new LinearAxis(pTransform1, ChartObj.Y_AXIS);

yAxis2.SetAxisIntercept(xAxis.GetAxisMax());

yAxis2.SetAxisTickDir(ChartObj.AXIS_MAX);

yAxis2.SetColor(Color.White);

chartVu.AddChartObject(yAxis2);

[VB]

Dim xAxis As New TimeAxis(pTransform1)

xAxis.SetColor(Color.White)

chartVu.AddChartObject(xAxis)

Dim yAxis As New LinearAxis(pTransform1, ChartObj.Y_AXIS)

‘ Default places y-axis at miniumum of x-coordinate scale

yAxis.SetColor(Color.White)

chartVu.AddChartObject(yAxis)

Dim yAxis2 As New LinearAxis(pTransform1, ChartObj.Y_AXIS)

yAxis2.SetAxisIntercept(xAxis.GetAxisMax())

yAxis2.SetAxisTickDir(ChartObj.AXIS_MAX)

yAxis2.SetColor(Color.White)

chartVu.AddChartObject(yAxis2)

The other common reason to have multiple axes in a chart is to delineate the simultaneous use of different coordinate systems in the chart. In this case each coordinate system has an x- and/or y-axis to differentiate it from the other coordinate systems. When the different coordinate systems are created, they usually overlay the same area of the chart. The default positioning of the axes for each coordinate system will all overlay one another, making the axes unreadable. In the y-axis case you will want to offset additional axes to the left, or to the right of the default axis position, using the SetAxisIntecept method. When using the SetAxisIntercept method, make sure you specify the position using the units of the coordinate system scale at right angles to the axis. Specify an intercept value outside of the normal scale range to offset the axes so that they do not overlap. The example below, extracted from the MultiAxes example, creates one x-axis, common to all of the charts because the x-scaling for all of the coordinate systems match, and five y-axes, one for each of the five different coordinate systems.

[C#]

CartesianCoordinates pTransform1;

CartesianCoordinates pTransform2;

CartesianCoordinates pTransform3;

CartesianCoordinates pTransform4;

CartesianCoordinates pTransform5;

. // Initialize datasets, coordinate system ranges

// The x-scale range for pTransform1 to pTransform5 are all the same, 0 - 100

// The y-scale range for pTransform1 to pTransform5 are all different

// The plotting area for each pTransform is indentical, leaving a large open

// to the left for extra axes.

pTransform1.SetGraphBorderDiagonal(0.35, .15, .9, 0.65) ;

pTransform2.SetGraphBorderDiagonal(0.35, .15, .9, 0.65) ;

pTransform3.SetGraphBorderDiagonal(0.35, .15, .9, 0.65) ;

pTransform4.SetGraphBorderDiagonal(0.35, .15, .9, 0.65) ;

pTransform5.SetGraphBorderDiagonal(0.35, .15, .9, 0.65) ;

ChartAttribute attrib1 = new ChartAttribute (Color.Blue, 2,DashStyle.Solid);

ChartAttribute attrib2 = new ChartAttribute (Color.Red, 2,DashStyle.Solid);

ChartAttribute attrib3 = new ChartAttribute (Color.Green, 2,DashStyle.Solid);

ChartAttribute attrib4 = new ChartAttribute (Color.Orange, 2,DashStyle.Solid);

ChartAttribute attrib5 = new ChartAttribute (Color.Magenta, 2,DashStyle.Solid);

xAxis = new LinearAxis(pTransform1, ChartObj.X_AXIS);

xAxis.SetLineWidth(2);

chartVu.AddChartObject(xAxis);

yAxis1 = new LinearAxis(pTransform1, ChartObj.Y_AXIS);

yAxis1.SetAxisIntercept(0.0);

yAxis1.SetChartObjAttributes(attrib1); // axis color matches line color

chartVu.AddChartObject(yAxis1);

yAxis2 = new LinearAxis(pTransform2, ChartObj.Y_AXIS);

yAxis2.SetAxisIntercept(-18);

yAxis2.SetChartObjAttributes(attrib2); // axis color matches line color

chartVu.AddChartObject(yAxis2);

yAxis3 = new LinearAxis(pTransform3, ChartObj.Y_AXIS);

yAxis3.SetAxisIntercept(-35);

yAxis3.SetChartObjAttributes(attrib3); // axis color matches line color

chartVu.AddChartObject(yAxis3);

yAxis4 = new LinearAxis(pTransform4, ChartObj.Y_AXIS);

yAxis4.SetAxisIntercept(-52);

yAxis4.SetChartObjAttributes(attrib4); // axis color matches line color

chartVu.AddChartObject(yAxis4);

yAxis5 = new LinearAxis(pTransform5, ChartObj.Y_AXIS);

yAxis5.SetAxisIntercept(xAxis.GetAxisMax());

yAxis5.SetAxisTickDir(ChartObj.AXIS_MAX);

yAxis5.SetChartObjAttributes(attrib5); // axis color matches line color

chartVu.AddChartObject(yAxis5);

NumericAxisLabels xAxisLab = new NumericAxisLabels(xAxis);

xAxisLab.SetTextFont(theFont);

chartVu.AddChartObject(xAxisLab);

NumericAxisLabels yAxisLab1 = new NumericAxisLabels(yAxis1);

yAxisLab1.SetTextFont(theFont);

yAxisLab1.SetAxisLabelsFormat(ChartObj.BUSINESSFORMAT);

chartVu.AddChartObject(yAxisLab1);

NumericAxisLabels yAxisLab2 = new NumericAxisLabels(yAxis2);

yAxisLab2.SetTextFont(theFont);

chartVu.AddChartObject(yAxisLab2);

NumericAxisLabels yAxisLab3 = new NumericAxisLabels(yAxis3);

yAxisLab3.SetTextFont(theFont);

chartVu.AddChartObject(yAxisLab3);

NumericAxisLabels yAxisLab4 = new NumericAxisLabels(yAxis4);

yAxisLab4.SetTextFont(theFont);

chartVu.AddChartObject(yAxisLab4);

NumericAxisLabels yAxisLab5 = new NumericAxisLabels(yAxis5);

yAxisLab5.SetTextFont(theFont);

chartVu.AddChartObject(yAxisLab5);

Font axisTitleFont = new Font("SansSerif", 10, FontStyle.Bold);

AxisTitle xaxistitle = new AxisTitle( xAxis, axisTitleFont, "Event Partition");

chartVu.AddChartObject(xaxistitle);

Grid xgrid = new Grid(xAxis, yAxis1,ChartObj.X_AXIS, ChartObj.GRID_MAJOR);

chartVu.AddChartObject(xgrid);

SimpleLinePlot thePlot1 = new SimpleLinePlot(pTransform1, Dataset1, attrib1);

chartVu.AddChartObject(thePlot1);

SimpleLinePlot thePlot2 = new SimpleLinePlot(pTransform2, Dataset2, attrib2);

chartVu.AddChartObject(thePlot2);

SimpleLinePlot thePlot3 = new SimpleLinePlot(pTransform3, Dataset3, attrib3);

chartVu.AddChartObject(thePlot3);

SimpleLinePlot thePlot4 = new SimpleLinePlot(pTransform4, Dataset4, attrib4);

chartVu.AddChartObject(thePlot4);

SimpleLinePlot thePlot5 = new SimpleLinePlot(pTransform5, Dataset5, attrib5);

chartVu.AddChartObject(thePlot5);

[VB]

Dim pTransform1 As CartesianCoordinates

Dim pTransform2 As CartesianCoordinates

Dim pTransform3 As CartesianCoordinates

Dim pTransform4 As CartesianCoordinates

Dim pTransform5 As CartesianCoordinates

Dim xAxis As LinearAxis

Dim yAxis1 As LinearAxis

Dim yAxis2 As LinearAxis

Dim yAxis3 As LinearAxis

Dim yAxis4 As LinearAxis

Dim yAxis5 As LinearAxis

. ‘ Initialize datasets, coordinate system ranges

‘ The x-scale range for pTransform1 to pTransform5 are all the same, 0 - 100

‘ The y-scale range for pTransform1 to pTransform5 are all different

pTransform1.SetGraphBorderDiagonal(0.35, 0.15, 0.9, 0.65)

pTransform2.SetGraphBorderDiagonal(0.35, 0.15, 0.9, 0.65)

pTransform3.SetGraphBorderDiagonal(0.35, 0.15, 0.9, 0.65)

pTransform4.SetGraphBorderDiagonal(0.35, 0.15, 0.9, 0.65)

pTransform5.SetGraphBorderDiagonal(0.35, 0.15, 0.9, 0.65)

Dim background As New Background(pTransform1,

ChartObj.GRAPH_BACKGROUND, Color.White)

chartVu.AddChartObject(background)

Dim attrib1 As New ChartAttribute(Color.Blue, 2, DashStyle.Solid)

Dim attrib2 As New ChartAttribute(Color.Red, 2, DashStyle.Solid)

Dim attrib3 As New ChartAttribute(Color.Green, 2, DashStyle.Solid)

Dim attrib4 As New ChartAttribute(Color.Orange, 2, DashStyle.Solid)

Dim attrib5 As New ChartAttribute(Color.Magenta, 2, DashStyle.Solid)

xAxis = New LinearAxis(pTransform1, ChartObj.X_AXIS)

xAxis.SetLineWidth(2)

chartVu.AddChartObject(xAxis)

yAxis1 = New LinearAxis(pTransform1, ChartObj.Y_AXIS)

yAxis1.SetAxisIntercept(0.0)

yAxis1.SetChartObjAttributes(attrib1) ' axis color matches line color

chartVu.AddChartObject(yAxis1)

yAxis2 = New LinearAxis(pTransform2, ChartObj.Y_AXIS)

yAxis2.SetAxisIntercept(-18)

yAxis2.SetChartObjAttributes(attrib2) ' axis color matches line color

chartVu.AddChartObject(yAxis2)

yAxis3 = New LinearAxis(pTransform3, ChartObj.Y_AXIS)

yAxis3.SetAxisIntercept(-35)

yAxis3.SetChartObjAttributes(attrib3) ' axis color matches line color

chartVu.AddChartObject(yAxis3)

yAxis4 = New LinearAxis(pTransform4, ChartObj.Y_AXIS)

yAxis4.SetAxisIntercept(-52)

yAxis4.SetChartObjAttributes(attrib4) ' axis color matches line color

chartVu.AddChartObject(yAxis4)

yAxis5 = New LinearAxis(pTransform5, ChartObj.Y_AXIS)

yAxis5.SetAxisIntercept(xAxis.GetAxisMax())

yAxis5.SetAxisTickDir(ChartObj.AXIS_MAX)

yAxis5.SetChartObjAttributes(attrib5) ' axis color matches line color

chartVu.AddChartObject(yAxis5)

Dim xAxisLab As New NumericAxisLabels(xAxis)

xAxisLab.SetTextFont(theFont)

chartVu.AddChartObject(xAxisLab)

Dim yAxisLab1 As New NumericAxisLabels(yAxis1)

yAxisLab1.SetTextFont(theFont)

yAxisLab1.SetAxisLabelsFormat(ChartObj.BUSINESSFORMAT)

chartVu.AddChartObject(yAxisLab1)

Dim yAxisLab2 As New NumericAxisLabels(yAxis2)

yAxisLab2.SetTextFont(theFont)

chartVu.AddChartObject(yAxisLab2)

Dim yAxisLab3 As New NumericAxisLabels(yAxis3)

yAxisLab3.SetTextFont(theFont)

chartVu.AddChartObject(yAxisLab3)

Dim yAxisLab4 As New NumericAxisLabels(yAxis4)

yAxisLab4.SetTextFont(theFont)

chartVu.AddChartObject(yAxisLab4)

Dim yAxisLab5 As New NumericAxisLabels(yAxis5)

yAxisLab5.SetTextFont(theFont)

chartVu.AddChartObject(yAxisLab5)

Dim axisTitleFont As New Font("SansSerif", 10, FontStyle.Bold)

Dim xaxistitle As New AxisTitle(xAxis, axisTitleFont, "Event Partition")

chartVu.AddChartObject(xaxistitle)

Dim xgrid As New Grid(xAxis, yAxis1, ChartObj.X_AXIS, ChartObj.GRID_MAJOR)

chartVu.AddChartObject(xgrid)

Dim thePlot1 As New SimpleLinePlot(pTransform1, Dataset1, attrib1)

chartVu.AddChartObject(thePlot1)

Dim thePlot2 As New SimpleLinePlot(pTransform2, Dataset2, attrib2)

chartVu.AddChartObject(thePlot2)

Dim thePlot3 As New SimpleLinePlot(pTransform3, Dataset3, attrib3)

chartVu.AddChartObject(thePlot3)

Dim thePlot4 As New SimpleLinePlot(pTransform4, Dataset4, attrib4)

chartVu.AddChartObject(thePlot4)

Dim thePlot5 As New SimpleLinePlot(pTransform5, Dataset5, attrib5)

chartVu.AddChartObject(thePlot5)

4. Can I add new axes, text objects, plot objects, and images to a chart after it is already displayed; or must I create a new chart from scratch taking into account the additional objects?

There are two ways to add new objects to a chart. The first way is to create all objects when the chart is initially created, but disable the ones that you do not want to show up when the chart is initially rendered. Enable the objects when you want them to show up. Use the chart objects SetChartObjEnable method to enable/disable the object. This is useful if you are creating an animated chart where you want the chart to sequence through a predefined series of steps. The second way you add new chart objects to the ChartView using the ChartView.AddChartObject method. In both cases you need to call the ChartView.UpdateDraw() method after any changes are made.

The example below, extracted from the the CustomChartDataCursor class, creates a new Marker object and NumericLabel object each time a mouse button clicked.

[C#]

Marker amarker = new Marker(GetChartObjScale(), MARKER_BOX,

nearestPoint.GetX(), nearestPoint.GetY(), 10.0, PHYS_POS);

chartVu.AddChartObject(amarker);

rNumericLabelCntr += 1.0;

// Add a numeric label the identifies the marker

pointLabel = new NumericLabel(GetChartObjScale(),

textCoordsFont, rNumericLabelCntr, nearestPoint.GetX(),

nearestPoint.GetY(), PHYS_POS, DECIMALFORMAT, 0);

// Nudge text to the right and up so that it does not write over marker

pointLabel.SetTextNudge(5,-5);

chartVu.AddChartObject(pointLabel);

chartVu.UpdateDraw();

[VB]

Dim amarker As New Marker(GetChartObjScale(), MARKER_BOX, nearestPoint.GetX(),

nearestPoint.GetY(), 10.0, PHYS_POS)

chartview.AddChartObject(amarker)

rNumericLabelCntr += 1.0

‘ Add a numeric label the identifies the marker

pointLabel = New NumericLabel(GetChartObjScale(), textCoordsFont,

rNumericLabelCntr, nearestPoint.GetX(), nearestPoint.GetY(),

PHYS_POS, DECIMALFORMAT, 0)

' Nudge text to the right and up so that it does not write over marker

pointLabel.SetTextNudge(5, -5)

chartview.AddChartObject(pointLabel)

chartview.UpdateDraw()

5. How do you zoom charts that use multiple coordinate systems?

The ChartZoom class will zoom one or more simultaneous coordinate systems. The example program SuperZoom zooms a chart that has one x-axis and five y-axes. Use the ChartZoom constructor that accepts an array of coordinate system objects.

6. How do you handle missing data points in a chart?

There are two ways to handle missing, or bad data. The first is to mark the data point in the dataset invalid, using the datasets SetValidData method. The second is to set the x- and/or y- value of the bad data point to the designated bad data value, ChartObj.rBadDataValue. Currently this value is set equal to the value of System.Double.MaxValue. Either method will prevent the data point from being displayed in a chart. If the bad data value is part of a line plot, a gap will appear in the line plot at that point. Bad data points are not deleted from a dataset.

7. How do you update a chart in real-time?

n general, real-time updates involve adding new objects to a chart, or modifying existing objects that are already in the chart. Once the object is added or changed, call the ChartView.UpdateDraw() method to force the chart to update using the new values. Objects can be added or modified based on some external event, or in response to a timer event created using System.Timers.Timer. Make all changes for a given event and call the ChartView.UpdateDraw method once. The position of most GraphObj derived objects is set or modified using one of the objects SetLocation methods. New data points can be added to an existing dataset using one of the datasets AddDataPoint, AddTimeDataPoint, AddGroupDataPoints or AddTimeGroupDataPoints methods. ChartPlot derived objects that use datasets will update to reflect the new values when the ChartView.UpdateDraw method is called. If the coordinates of the new data points are outside of the x- and y-limits of the current coordinate system it may be necessary to rescale the coordinate system so that the new points show up; otherwise the new data points will be clipped. The new scale values can be set explicitly, or calculated using one of the auto-scale methods. The example programs SpectrumAnalyzer, DataLogger, DynPieChart and ScrollingMixedPlot all demonstrate various ways to update charts in real-time.

If you want to change points in an existing dataset, but not the size of the dataset, call the datasets appropriate SetXDataValue, SetYDataValue, or SetDataPoint methods. The dataset has its own copy of the data so you must change these values, not the original values you used to initialize the dataset. If you plan to change every value in the dataset, you can do that point by point, or create a new dataset and swap that in for the old dataset using the plot objects SetDataset or SetGroupDataset method. Call the ChartView.UpdateDraw method to force the chart to update using the new values.

8. How do I prevent flicker when updating my charts on real-time?

Flicker is the result of erasing and redrawing all or part of a chart in the current display buffer. Double buffering of screen images can minimize any flicker. The ChartView class does the actual work of rendering a chart image to the underlying Control display buffer. The ChartView class uses double buffering for the display of all screen images. When a chart is updated it is automatically rendered to an off-screen bitmap. When drawing is complete the off-screen bitmap is copied to the screen display buffer, minimizing the effect of flicker..

9. How do you implement drill down, or data tooltips in a chart?

Implementing drill down or tooltips consists of three major parts:

· Trapping a mouse event and determining the mouse cursor position in device and physical coordinates.

· Identifying the chart object that intersects the mouse event.

· Displaying appropriate information about the chart object.

There are many classes that aid in one or more of these functions. The MouseListener class will trap a mouse event in the chart view. The FindObj class will filter and return the chart object, if any, that intersects the mouse cursor when a mouse button is pressed. The MoveObj class will filter, select and move a chart object as the mouse is dragged across the chart. The DataToolTip class will find the data point in a chart nearest the mouse cursor and display xy information about the data point as a popup ChartText display. The DataToolTip can also be customized for the display of custom information about the selected data point. It only takes a few lines to add a simple y-value tooltip to an existing chart.

[C#]

DataToolTip datatooltip = new DataToolTip(chartVu);

datatooltip.SetEnable(true);

chartVu.SetCurrentMouseListener(datatooltip);

[Visual Basic]

Dim datatooltip As New DataToolTip(chartVu)

datatooltip.SetEnable(True)

chartVu.SetCurrentMouseListener(datatooltip)

Some of the example programs that include tooltips include LineFill, Multiline, LinePlotSegments, StackedLineChart, Logarithmic, SimpleBarChart, GroupBarPlotChart, DoubleBarPlot, OpeningScreen, OHLCFinPlot and LabeledPieChart.

10. I do not want to my graph to auto-scale. How do I setup the graph axes for a specific range?

Auto-scaling has two parts. The first is the auto-scaling of the coordinate system based on one or more datasets. The second part is the auto-scaling of the axes that reside in the coordinate system. Manually scale the coordinate system and axes by calling the appropriate constructors. For example:

[C#]

ChartCalendar xMin = new ChartCalendar(1996, ChartObj.FEBRUARY, 5);

ChartCalendar xMax = new ChartCalendar(2002, ChartObj.JANUARY, 5);

double yMin = 0;

double yMax = 105;

TimeCoordinates simpleTimeScale;

simpleTimeScale = new TimeCoordinates(xMin, yMin, xMax, yMax);

// Create the time axis (x-axis is assumed)

TimeAxis xAxis = new TimeAxis(simpleTimeScale);

// Create the linear y-axis

LinearAxis yAxis = new LinearAxis(simpleTimeScale, ChartObj.Y_AXIS);

// Create the ChartView object to place graph objects in.

ChartView chartVu = new ChartView();

// Add the x- and y-axes to the chartVu object

chartVu.AddChartObject(xAxis);

chartVu.AddChartObject(yAxis);

[Visual Basic]

Dim xMin As ChartCalendar = New ChartCalendar(1996, ChartObj.FEBRUARY, 5)

Dim xMax As ChartCalendar = New ChartCalendar(2002, ChartObj.JANUARY, 5)

Dim yMin As Double = 0

Dim yMax As Double = 105

Dim simpleTimeScale As TimeCoordinates

simpleTimeScale = New TimeCoordinates(xMin, yMin, xMax, yMax)

' Create the time axis (x-axis is assumed)

Dim xAxis As TimeAxis = New TimeAxis(simpleTimeScale)

' Create the linear y-axis

Dim yAxis As LinearAxis = New LinearAxis(simpleTimeScale, ChartObj.Y_AXIS)

' Create the ChartView object to place graph objects in.

Dim chartVu As ChartView = New ChartView()

' Add the x- and y-axes to the chartVu object

chartVu.AddChartObject(xAxis)

chartVu.AddChartObject(yAxis)

The documentation for the various coordinate system and axis classes includes examples of manual scaling.

11. How do I update my data, and auto-rescale the chart scales and axes to reflect the new data, after it has already been drawn?

Updating data was discussed in FAQ # 6. If you want the chart to rescale based on the new data, call the appropriate coordinate systems auto-scale method, followed by the auto-axis methods of all related axes. Then call the ChartView.UpdateDraw method. For example:

[C#]

// Create the ChartView object to place graph objects in.

TimeSimpleDataset Dataset1 = new TimeSimpleDataset("Sales",x1,y1);

TimeCoordinates simpleTimeCoordinates = new TimeCoordinates();

simpleTimeCoordinates.AutoScale(Dataset1,

ChartObj.AUTOAXES_FAR , ChartObj.AUTOAXES_FAR);

ChartView chartVu = new ChartView();

// Create the time axis (x-axis is assumed)

TimeAxis xAxis = new TimeAxis(simpleTimeCoordinates);

// Create the linear y-axis

LinearAxis yAxis = new LinearAxis( simpleTimeCoordinates, ChartObj.Y_AXIS);

// The following code would be in the code handling the rescale event

// Rescale chart based on a modified Dataset1 datset

simpleTimeCoordinates.AutoScale(Dataset1,

ChartObj.AUTOAXES_FAR , ChartObj.AUTOAXES_FAR);

xAxis.CalcAutoAxis();

yAxis.CalcAutoAxis();

// Redraw the chart using the rescaled coordinate system and axes

chartVu.UpdateDraw();

[Visual Basic]

Dim Dataset1 As TimeSimpleDataset = New TimeSimpleDataset("Sales", x1, y1)

Dim simpleTimeCoordinates As TimeCoordinates = New TimeCoordinates()

simpleTimeCoordinates.AutoScale(Dataset1, ChartObj.AUTOAXES_FAR, _

ChartObj.AUTOAXES_FAR)

Dim chartVu As ChartView = New ChartView()

' Create the time axis (x-axis is assumed)

Dim xAxis As TimeAxis = New TimeAxis(simpleTimeCoordinates)

' Create the linear y-axis

Dim yAxis As LinearAxis = New LinearAxis(simpleTimeCoordinates, ChartObj.Y_AXIS)

' The following code would be in the code handling the rescale event

' Rescale chart based on a modified Dataset1 datset

simpleTimeCoordinates.AutoScale(Dataset1, ChartObj.AUTOAXES_FAR, _

ChartObj.AUTOAXES_FAR)

xAxis.CalcAutoAxis()

yAxis.CalcAutoAxis()

' Redraw the chart using the rescaled coordinate system and axes

chartVu.UpdateDraw()

12. When I use the auto-scale and auto-axis routines my semi-log chart has the log axis scaled using powers of 10 (1, 10,100, 1000, etc.) as the starting and ending values, or as the major tick interval for labeling. How do I make my log graphs start at 20 and end at 50,000, with major tick marks at 20, 200, 2000 and 20000?

The auto-scale routines for logarithmic coordinate systems will always select a power of 10 for the minimum and maximum value of the scale. You can use the auto-scale routine and then override the minimum and/or maximum values for the logarithmic scale. The default LogAxis constructor will pick up on the minimum of the coordinate system and use that as the axis tick mark origin. Or you can leave the coordinate system unchanged, and change the starting point of the axis tick marks using the axis SetAxisTickOrigin method. The example below is derived from the Logarithmic example code.

[C#]

GroupDataset Dataset1 = new GroupDataset("First",x1,y1);

CartesianCoordinates pTransform1 = new CartesianCoordinates(ChartObj.LOG_SCALE,

ChartObj.LINEAR_SCALE);

pTransform1.AutoScale(Dataset1, ChartObj.AUTOAXES_FAR, ChartObj.AUTOAXES_FAR);

pTransform1.SetScaleStartX(20); // Force start of scale at 20, AutoScale will

// always choose a power of 10 decade.

LogAxis xAxis = new LogAxis(pTransform1, ChartObj.X_AXIS);

xAxis.SetAxisTickOrigin(20);

chartVu.AddChartObject(xAxis);

[Visual Basic]

' Create the ChartView object to place graph objects in.

Dim Dataset1 As GroupDataset = New GroupDataset("First", x1, y1)

Dim pTransform1 As CartesianCoordinates = _

New CartesianCoordinates(ChartObj.LOG_SCALE, ChartObj.LINEAR_SCALE)

pTransform1.AutoScale(Dataset1, ChartObj.AUTOAXES_FAR, ChartObj.AUTOAXES_FAR)

pTransform1.SetScaleStartX(20) ' Force start of scale at 20, AutoScale will

' always choose a power of 10 decade.

Dim xAxis As LogAxis = New LogAxis(pTransform1, ChartObj.X_AXIS)

xAxis.SetAxisTickOrigin(20)

chartVu.AddChartObject(xAxis)

13. How do I create and use custom, multi-line string labels as the axis labels for my graph?

The StringAxisLabels class should be used to create multi-line axis labels. Insert the “\n” new line character to add additional lines to each string used to define the string axis labels. The example below is from the AxisLabels example program.

[C#]

String []xstringlabels =

{

"",

"Western"+"\n"+"Sales"+"\n"+"Region",

"Eastern"+"\n"+"Sales"+"\n"+"Region",

"Southern"+"\n"+"Sales"+"\n"+"Region",

"Northern"+"\n"+"Sales"+"\n"+"Region"};

StringAxisLabels xAxisLab5 = new StringAxisLabels(xAxis5);

xAxisLab5.SetAxisLabelsStrings(xstringlabels,5);

xAxisLab5.SetTextFont(graph5Font);

chartVu.AddChartObject(xAxisLab5);

[Visual Basic]

Dim xstringlabels As [String]() = {"", "Western" + ControlChars.Lf + "Sales" + _

ControlChars.Lf + "Region", "Eastern" + ControlChars.Lf + "Sales" + _

ControlChars.Lf + "Region", "Southern" + ControlChars.Lf + "Sales" + _

ControlChars.Lf + "Region", "Northern" + ControlChars.Lf + "Sales" + _

ControlChars.Lf + "Region"}

Dim xAxisLab5 As New StringAxisLabels(xAxis5)

xAxisLab5.SetAxisLabelsStrings(xstringlabels, 5)

xAxisLab5.SetTextFont(graph5Font)

chartVu.AddChartObject(xAxisLab5)

14. How do I place more than one graph in a view?

One way to create multiple charts is to create multiple instances of the ChartView class and add each ChartView object to a container object such as a Control. A layout manager manages the position and size of each ChartView. Another way is to place multiple charts in the same ChartView object. This makes it easier to guarantee alignment between the axes of separate graphs. The trick to doing this is to create separate coordinate system objects (CartesianCoordinates, TimeCoordinates or PolarCoordinates) for each chart, and to position the plot area of each coordinate system so that they do not overlap. Use one of the coordinate systems SetGraphBorder… methods. Many of the examples use this technique, including GroupBarPlotChart, DoubleBarPlot, OHLFinPlot, FinOptions, DynPieChart, PieAndLineChart and PieAndBarChart. The example below was extracted from the OHLCFinPlot class.

[C#]

pTransform1 = new TimeCoordinates();

pTransform1.SetGraphBorderDiagonal(0.1, .15, .90, 0.6) ;

pTransform2 = new TimeCoordinates();

pTransform2.SetGraphBorderDiagonal(0.1, .7, .90, 0.875) ;

[Visual Basic]

pTransform1 = new TimeCoordinates()

pTransform1.SetGraphBorderDiagonal(0.1, .15, .90, 0.6)

pTransform2 = new TimeCoordinates()

pTransform2.SetGraphBorderDiagonal(0.1, .7, .90, 0.875)

15. How do I use the QCChart2D CF software to generate JPG, DIB, BMP, GIF, EMF, WMF, etc. files?

The .Net Compact Framework does not support the imaging routines needed to save charts as bitmap image files or metafiles. If you need to save charts as image files or metafiles you should be using the related product, QCChart2D for .Net.

16. Sometimes the major tick marks of an axis are missing the associated tick mark label ?

The axis labeling routines are quite intelligent. Before the label is drawn at its calculated position, the software does a check to see if the bounding box of the new axis label intersects the bounding box of the previous axis label. If the new label is going to overlap the previous label, the label is skipped. You can override this default behavior by calling the objects SetOverlapLabelMode method.

SetOverlapLabelMode (ChartObj.OVERLAP_LABEL_DRAW);

Another option, for horizontal axes only, is to stagger the tick mark labels. A stagger automatically alternates the line on which the tick mark label is placed.

SetOverlapLabelMode (ChartObj.OVERLAP_LABEL_STAGGER);

17. How do I change the order the chart objects are drawn? For example, I want one of my grid objects to be drawn under the charts line plot objects, and another grid object to be drawn top of the charts line plot objects.

There are two ordering methods used to render chart objects. The first method renders the objects in order, as added to the ChartView object. Objects added to the view last are drawn on top of objects added first. The second method renders the objects according to their z-order. Objects with the lowest z-order values are rendered first. Objects with equal z-order values are rendered in the ordered they are added to the ChartView object. The second method (z-order rendering) is the default method of object rendering used by the ChartView class. This default behavior can be changed by call the ChartView.SetZOrderSortEnable(false) method.

You can change the default z-order value on an object-by-object basis. Call the GraphObj.SetZOrder method to change the z-order for any given object.

See the section in the manual titled Rendering Order of GraphObj Objects for information about the default z-values for all chart objects

The example below sets the z-order value of grid1 to something less than the default value (50) of ChartPlot objects, and the z-order value of grid2 to something greater than the default value.

[C#]

ChartView chartVu = new ChartView();

Grid grid1 = new Grid(xAxis, yAxis, ChartObj.Y_AXIS, ChartObj.GRID_MAJOR);

grid1.SetZOrder(40); // This is actually the default value for the grid z-order

chartVu.AddChartObject(grid1);

Grid grid2 = new Grid(xAxis, yAxis, ChartObj.Y_AXIS, ChartObj.GRID_MINOR);

grid2.SetZOder(150); // Grid is drawn after ChartPlot objects

// which have default z-value of 50

chartVu.AddChartObject(grid2);

[Visual Basic]

Dim chartVu As ChartView = new ChartView()

Dim grid1 As Grid = new Grid(xAxis, yAxis, ChartObj.Y_AXIS, ChartObj.GRID_MAJOR)

grid1.SetZOrder(40) ‘ This is actually the default value for the grid z-order

chartVu.AddChartObject(grid1)

Dim grid2 As Grid = new Grid(xAxis, yAxis, ChartObj.Y_AXIS, ChartObj.GRID_MINOR)

grid2.SetZOder(150) ‘ Grid is drawn after ChartPlot objects

‘ which have default z-value of 50

chartVu.AddChartObject(grid2)

18. How to I use a ScrollBar object to control horizontal scrolling of the data in my chart?

You can place the ChartView object and the scroll bar in a parent container and use a layout manager to position everything. If you place the scroll bar in the ChartView you can still position it using a layout manager. The ChartView will always use the entire content area of the underlying Control for its canvas and the scroll bars will sit on top of this, not side by side. The example program LinePlotScrollBar uses two scroll bars, a horizontal scroll bar to control scrolling of the x-axis, and a vertical scroll bar that controls the magnitude of the y-axis. You need to add hScrollBar1_Scroll and vScrollBar1_Scroll event listeners to the ChartView class to process changes in scroll bar values.

As of this writing there seems to be serious problems with the .Net scrollbars, largely due to the circumstance that they do not support trapping MouseDown and MouseUp events. Since .Net Compact Framework devices are relatively slow, you do not want to place CPU intensive code in the HScrollBar1.ValueChanged (or VScrollBar1.ValueChanged) event handler, as we do in the regular .Net version of QCChart2D. This is because that event is triggered for evey pixel change in the value of the scrollbar, causing it to get bogged down when you try and move the scrollbar. A better technique is to only process changes in the graph when the MouseUp event is triggered by the scrollbar, signifying that the scroll operation is complete. But as we said, the MouseUp events don’t work. So we cheat, when a scrollbar value changes, we start a timer and only update the graph one second after the intial change. This gives the user time to complete the scrollbar movement and does not bog things down with multiple updates of the graph for intermediate values.

[C#]

public void UpdateXScaleAndAxes(int index)

{

int startindex = index;

pTransform1.SetScaleStartX( (double) startindex);

pTransform1.SetScaleStopX( (double) (startindex + 50));

xAxis.CalcAutoAxis();

yAxis.CalcAutoAxis();

xAxisLab.CalcAutoAxisLabels();

yAxisLab.CalcAutoAxisLabels();

this.UpdateDraw();

}

public void UpdateYScaleAndAxes(int index)

{

int startindex = index;

pTransform1.SetScaleStartY( (double) -startindex);

pTransform1.SetScaleStopY( (double) startindex);

xAxis.CalcAutoAxis();

yAxis.CalcAutoAxis();

xAxisLab.CalcAutoAxisLabels();

yAxisLab.CalcAutoAxisLabels();

this.UpdateDraw();

}

private void hScrollBar1_ValueChanged(object sender, System.EventArgs e)

{

hScrollActive = true;

this.timer1.Enabled = true;

}

private void vScrollBar1_ValueChanged(object sender, System.EventArgs e)

{

vScrollActive = true;

this.timer1.Enabled = true;

}

private void timer1_Tick(object sender, System.EventArgs e)

{

if (hScrollActive)

{

UpdateXScaleAndAxes(hScrollBar1.Value);

hScrollActive = false;

}

if (vScrollActive)

{

UpdateYScaleAndAxes( vScrollBar1.Value);

vScrollActive = false;

}

this.timer1.Enabled = false;

}

[Visual Basic]

Public Sub UpdateXScaleAndAxes(ByVal index As Integer)

Dim startindex As Integer = index

pTransform1.SetScaleStartX(CDbl(startindex))

pTransform1.SetScaleStopX(CDbl(startindex + 50))

xAxis.CalcAutoAxis()

yAxis.CalcAutoAxis()

xAxisLab.CalcAutoAxisLabels()

yAxisLab.CalcAutoAxisLabels()

Me.UpdateDraw()

End Sub 'UpdateXScaleAndAxes

Public Sub UpdateYScaleAndAxes(ByVal index As Integer)

Dim startindex As Integer = index

pTransform1.SetScaleStartY(CDbl(-startindex))

pTransform1.SetScaleStopY(CDbl(startindex))

xAxis.CalcAutoAxis()

yAxis.CalcAutoAxis()

xAxisLab.CalcAutoAxisLabels()

yAxisLab.CalcAutoAxisLabels()

Me.UpdateDraw()

End Sub 'UpdateYScaleAndAxes

Private Sub HScrollBar1_Scroll(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles HScrollBar1.ValueChanged

hScrollActive = True

Me.Timer1.Enabled = True

End Sub

Private Sub VScrollBar1_Scroll(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles VScrollBar1.ValueChanged

vScrollActive = True

Me.Timer1.Enabled = True

End Sub

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick

If (hScrollActive) Then

UpdateXScaleAndAxes(HScrollBar1.Value)

hScrollActive = False

End If

If (vScrollActive) Then

UpdateYScaleAndAxes(VScrollBar1.Value)

vScrollActive = False

End If

Me.Timer1.Enabled = False

End Sub

There are other examples of Form components interacting with charts. In the OHLCFinPlot example a Scrollbar controls the time axis of a stock market OHLC chart. The MultiAxes example uses Button objects to select the x-axis range.

19. I am trying to plot 100,000 data points and it takes too long to draw the graph. What is wrong with the software and what can I do to make it faster?
The software runs as fast as we can make it. We do not have any hidden switches that will speed up the software. What you need to do is to step back and think about the best way to display your data.
A fundamental issue that many programmers fail to consider is the relationship between the resolution of the rasterized screen image of the plot and the resolution of the data. A typical mobil device chart image will have 300-600 pixels as the horizontal resolution of the plotting area. This would imply that in the 100K data point example above, every horizontal pixel would represent 1.6K to 3.3K data points. Obviously this is a terrible mismatch. In fact it is a bad match for datasets that have more than a couple of thousands points.
So what you do is compress the data before it is displayed. Take the 100K data points and compress them down to 500 data points. The data compression can take several forms. You can take an average of every N points. The resulting dataset will be reduced by a factor of N. You can also find the sum for every N points, the minimum value of every N points, the maximum of every N points, or both the minimum and maximum of every 2N points. The last compression method, minimum and maximum, will always capture any minimums and maximum in the data. The result is a 1000 point compressed dataset, where there are at least two data points per pixel of horizontal resolution, will look just like the 100K point dataset, only display a hundred of times faster. The Datset classes all include compression methods (SimpleDataset.CompressSimpleDataset, GroupDataset.CompressGroupDataset, TimeSimpleDataset.CompressTimeSimpleDataset and TimeGroupDataset.CompressTimeGroupDataset, TimeGroupDataset.CompressTimeFieldSimpleDataset, TimeGroupDataset.CompressTimeFieldGroupDataset) that operate on the existing dataset and return a new, compressed dataset. The CompressTimeFieldSimpleData and CompressTimeFieldGroupDataset are particular useful because they do not use a fixed sample size of N, instead they compress data so that adjacent time values are an increment of a specific time field (ChartObj.DAY_OF_YEAR, ChartObj.WEEK_OF_YEAR, ChartObj.MONTH, ChartObj.Year). Compressing data by month and year obviously requires a varying sample size.
Once created, connect the compressed dataset to the ChartPlot object used to display the dataset

20. How do I get data from my database into a chart?

The real question is: How do you get data from your database into a simple .Net program, storing sequential data values in data array variables. This is up to you and is independent of the charting software. We recommend that you use the SQL database classes that are part of .Net and study the documentation provide by Microsoft and other sources, such as the O’Reilly programming books. Once you can read individual data elements of your data base it is a trivial matter to place the numeric and calendar data into simple .Net array variables and from there plot the data.

21. Are you going to add additional real-time routines to the QCChart2D CF for the .Net Compact Framework library?

Yes, see the Real-Time Graphics Tools for .Net for the types of routines that we will be adding.

http://www.quinn-curtis.com/QCRTGraphProdPage.htm

22. Are you going to add 3D routines to the QCChart2D CF for the .Net Compact Framework library?

Probably not. 3D Graphics are popular in presentation charting applications because management types think that 3D charts in their PowerPoint presentations make the content more believable. In most implementations of 3D charting, the use of the 3^rd dimension adds nothing to, and often obscures, the information content of the chart. It also makes real-time updates and interactive zooming slower and less precise.

Also, we are not looking for new ways to make the .Net Compact Framework slower than it already is.

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