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Using a MS Chart Control in VC

Environment: VC++, charting The following is the description for using a MS Chart control in VC++. The diagram below will give you an idea of the chart we are going to make. Firstly, insert the chart control in your project using Project->Add Reference->Microsoft Chart Control. Next is populating the chart control. When I was working […]

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May 29, 2003

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Environment: VC++, charting

The following is the description for using a MS Chart control in VC++. The diagram below will give you an idea of the chart we are going to make.

Firstly, insert the chart control in your project using Project->Add Reference->Microsoft Chart Control.

Next is populating the chart control. When I was working with Visual Basic, I had used data source to pass data to the chart. But in VC++, I did not get the datasource method in the initial tries. So, I passed the chart data through a COleSafeArray. Thanks to J. L. Colson for illuminating the details in his article.

Here is the code snippet for that:

//First, create a safe array

  COleSafeArray saRet;

  SAFEARRAYBOUND sab[2];

  sab[0].cElements = noOfRows;    // give this exactly the number
                                  // of rows you display in your
                                  // chart
  sab[1].cElements = 5;           // number of columns + 1
                                  // (because the first column is
                                  // where we put the row labels -
                                  // in 1.1, 2.1, 3.1, 4,1, etc.

    sab[0].lLbound = sab[1].lLbound = 1;

  // Use the chart as the backdrop of the legend.
  m_ChartControl.SetShowLegend(TRUE);

  // Create the safe array...

  saRet.Create(VT_BSTR, 2, sab);

  long index[2] = {0,0};         // a 2D graph needs a 2D array as
                                 // an index array
  BSTR bstr;
  index[0]=1;

  FILEDETAILS filedetailsstruct; // this is just a datastructure
                                 // I used, pls see attached code
  CString cstemp;

  //m_filedetails is an STL list of filedetailsstruct

  //-----------------------------------------------------
  // in this loop, we populate the safe array
  //-----------------------------------------------------
  for(i=m_filedetails.begin();i!=m_filedetails.end();i++)
  {
    filedetailsstruct =(FILEDETAILS)*i;
    index[1]=1;
    bstr = filedetailsstruct.login.AllocSysString();  // Row label
    // make sure this cannot be converted to a valid number like
    // "54" and is a valid string like "John"

      saRet.PutElement(index, bstr);

      index[1]=2;

    bstr = filedetailsstruct.n9000.AllocSysString();
           // Data for column 1
    ::SysFreeString(bstr);
    saRet.PutElement(index, bstr);

    index[1]=3;
    bstr = filedetailsstruct.n9002.AllocSysString();
           // Data for column 2
    ::SysFreeString(bstr);
    saRet.PutElement(index, bstr);

    index[1]=4;
    bstr = filedetailsstruct.n9004.AllocSysString();
           // Data for column 3
    ::SysFreeString(bstr);
    saRet.PutElement(index, bstr);

    index[1]=5;
    bstr = filedetailsstruct.nCancel.AllocSysString();
           // Data for column 4
    ::SysFreeString(bstr);
    saRet.PutElement(index, bstr);

    index[0]++;

  }

// now hand over the safe array to the chart control

m_ChartControl.SetChartData(saRet.Detach());

Our chart data will look like this:

............................

2,1  2,2  2,3  2,4  2,5

1,1  1,2  1,3  1,4  1,5

where

1,1 -Row label 1
2,1 -Row Label 2

Okay, now to label the columns:

  m_ChartControl.SetColumnLabelCount(4);
  m_ChartControl.SetColumn(1);
  m_ChartControl.SetColumnLabel("Monday") ;
  m_ChartControl.SetColumn(2);
  m_ChartControl.SetColumnLabel("Wednesday") ;
  m_ChartControl.SetColumn(3);
  m_ChartControl.SetColumnLabel("Friday") ;
  m_ChartControl.SetColumn(4);
  m_ChartControl.SetColumnLabel("Saturday") ;