Measurement Studio for .NET Languages
Waveformgraph: Resuming plot from left of chart
Hello Chris,
Just to add to what Matt said, if you are trying to keep a constant 24 hour xAxis, and want to maintain the previous day's data while the current day's data plots, you could implement a sweep mode for the waveform graph, similar to what LabWindows/CVI and LabVIEW offer. Because Measurement Studio does not offer this functionality natively, you will have to add it yourself, but I have tried to simplify this for you with the following ideas and example program.
One possible way to implement this would be two have two plots for each channel of data you have. One plot would be responsible for the previous day's data, and the other would be responsible for plotting the current days data. This way, when one day completes, you switch your active plot to be the oldest plot, clear this oldest plot, and then commence plotting the current day's data. Once you have this implemented, all that is left to do (if you wish) is to make the previous day's data disappear as you plot the current day's data, resulting in a graph that looks similar to the following:
This feature is implemented by creating your own LineStyle class, inheriting from the National Instruments.UI.LineStyle class. You will then need to override the CreatePen method, as well as a few others. Below are the important snippets of code demonstrating this approach, with comments. Also, you will find the entire example attached below, so that you can examine it in it's entirety. Please let me know if this is not what you were looking for, or if you have any questions about any of the code.
The following is the code that swaps which plot is being used to actively plot data:
private void waveformGraph1_PlotDataChanged(object sender, XYPlotDataChangedEventArgs e)
{
xyCursor1.XPosition = counter;
if (counter >= 499) /* the end of the 'day' has been reached */
{
if (plotObject == waveformPlot1) /* switch plots */
{
disLineStyle.LineColor = plotObject.LineColor; /* switch the line color for the custom line style */
plotObject.LineStyle = disLineStyle; /* set the day old plot to the custom line style */
plotObject = waveformPlot2;
plotObject.LineStyle = LineStyle.Solid; /* reset the line style for the current plot */
xyCursor1.Plot = plotObject;
this.Text = "Using Waveform Plot 2...";
}
else
{
disLineStyle.LineColor = plotObject.LineColor;
plotObject.LineStyle = disLineStyle;
plotObject = waveformPlot1;
plotObject.LineStyle = LineStyle.Solid;
xyCursor1.Plot = plotObject;
this.Text = "Using Waveform Plot 1...";
}
counter = 0; /* reset your counter */
plotObject.ClearData(); /* clear the old data */
}
/* get the context coordinates of the currently plotted point, in order to know where to start erasing */
disLineStyle.TransitionPoint = plotObject.MapDataPoint(waveformGraph1.PlotAreaBounds, xyCursor1.XPosition, 0.0).X - waveformGraph1.PlotAreaBounds.X;
}
The following is the implementation of the custom line styles CreatePen method:
public override Pen CreatePen(object context, LineStyleDrawArgs args)
{
Rectangle bounds = args.ContextBounds;
/* Add 1 to width and height of context bounds to include */
/* the right and bottom edge of the rectangle in the linear */
/* gradient brush */
bounds.Width += 1;
bounds.Height += 1;
/* create a new linear brush to go from transparent to opaque */
using (LinearGradientBrush lBG = new LinearGradientBrush(bounds, Color.FromArgb(0, _lineColor), _lineColor, LinearGradientMode.Horizontal))
{
Blend blend = new Blend(); /* create a blend objet to make gradient instantaneous */
float transition = (float)_transitionPoint / (float)args.ContextBounds.Width;
float[] factors = {0.0f, 0.0f, 1.0f, 1.0f};
float[] positions = {0.0f, transition - .01f, transition, 1.0f}; /* make the gradient switch at the transition point */
blend.Factors = factors;
blend.Positions = positions;
lBG.Blend = blend;
return new Pen(lBG, args.Width);
}
}
For the rest of the implemenation, please see the attachment.
NickB
National Instruments
Hey Chris,
The reason the 'old' plots are changing to a single color is that they are all using the same DisappearingLineStyle object, disLineStyle. Thus, when you set the color of this custom line style:
disLineStyle.LineColor = Plot(Channel).LineColor
you are only ever updating one reference, and all of your 'old' plots are using that single reference. Just like you have to have multiple plots to have multiple colors, each plot will have to have it's own DisappearingLineStyle object in order have multiple colors when using the DisappearingLineStyle class. Your code may need to look something like this:
disLineStyle(Channel).LineColor = Plot(Channel).LineColor
Please let me know if I can be any more help.
NickB
National Instruments
