Tutorial: Create chart data

Create chart data

We now have data in our graph, but we want to make the graph a little more desirable, and so we will add left and bottom axes, and a title. We'll do this still inside the OnInitialUpdate member of our view class. Setting the title of the chart is simple.

	m_Chart.SetTitle( "A parabola" );

OK, so let's set up some axes. We need a pointer to a CAxis object, and then we call the CChart::AddAxis member function:

	CAxis	*axis;
	axis = m_Chart.AddAxis( kLocationLeft );

This adds a left hand axis, but we still need to set the title. That's why we have the axis pointer:

	axis->SetTitle( "Parabola Y Value" );

Now we'll add a bottom axis, and set its title:

	axis = m_Chart.AddAxis( kLocationBottom );
	axis->SetTitle( "X Value" );

What if we want to change something about the data set, such as markers or line thickness? You may recall that when we set the data, we used the function:

	dataID = m_Chart.AddData( data, nDims, dims );

which returns dataID. We use this dataID in order to change anything about the data set. Let's add some markers, and make them display every other data point:

	m_Chart.SetMarkerType( dataID, kXYMarkerSquare );
	m_Chart.SetMarkerFrequency( dataID, 2 );

With all of these lines added, your OnInitialUpdate function will look something like the following:

#define kDataSize 26
void CTestProjectView::OnInitialUpdate() 
{
	CView::OnInitialUpdate();

	int		data[2*kDataSize], i;
	int		nDims, dims[2];
	int		dataID;
	CAxis	*axis;
	
	for( i = 0; i < kDataSize; i++ )
	{
		// The X data
		data[i] = i - kDataSize/2;
		// The Y Data
		data[i  + kDataSize] = data[i]*data[i];
	}
	nDims = 2;
	dims[0] = 2; // Two dimensions along the first axis
	dims[1] = kDataSize; // kDataSize dimensions along the second
	dataID = m_Chart.AddData( data, nDims, dims );
	
	m_Chart.SetTitle( "A parabola" );
	axis = m_Chart.AddAxis( kLocationLeft );
	axis->SetTitle( "Parabola Y Value" );
	axis = m_Chart.AddAxis( kLocationBottom );
	axis->SetTitle( "X Value" );

	m_Chart.SetMarkerType( dataID, kXYMarkerSquare );
	m_Chart.SetMarkerFrequency( dataID, 2 );
}

And now that we have the chart set up, we need to know how to display the chart.

Tutorial:

CPlot Reference