(C++ VCL) TChart

Visual Component for visualizing data series.

Can be forward declarated with:

namespace Chart { class TChart; };

In the implementation file, #include chart.hpp:

include <Chart.hpp>

The TChart Component cannot plot a surface plot. You can use Bilderbikkel's SurfacePlotter class for this.

Note that the CLX library does NOT contain an equivalent of this Component.

How-to's overview:

How to: read the values from a TChart?
How to: calculate a best-fitting line of the values in a TChart?
How to: draw a best fitting line of a ChartSeries?

How to: read the values from a TChart?

include <assert>


//Fill the Chart with values
for (double x = 0.0; x < 10.0; x+=0.1234)
{
  const double y = x * x;
  Chart1->Series[0]->AddXY(x,y);
}
//Copy the pointers to the values
TChartValueList * xValues(Chart1->Series[0]->XValues);
TChartValueList * yValues(Chart1->Series[0]->YValues);
//Assume there are as many X's as Y's
assert(xValues->Count()==yValues->Count());
//Loop through them and put them in a TRichEdit
const int count = xValues->Count();
for (int i=0; i!=count; ++i)
{
  String myString = FloatToStr(xValues->operator [](i)) + " " + FloatToStr(yValues->operator [](i));
  RichEdit1->Lines->Add(myString);
}

How to: calculate a best-fitting line of the values in a TChart ?

void getTrendLine(const TChartSeries * series, double& offset, double& slope)
{
  const int nValues = (const_cast<TChartSeries*>(series))->Count(); //VCL is not const-correct
  //Calculate meanX and meanY
  double sumX = 0.0;
  double sumY = 0.0;
  for (int i=0; i!=nValues; ++i)
  {
    sumX += series->XValues->operator [](i);
    sumY += series->YValues->operator [](i);
  }
  const double meanX = sumX / static_cast<double>(nValues);
  const double meanY = sumY / static_cast<double>(nValues);
  double sumBup = 0.0;
  double sumBdown = 0.0;
  for (int i=0; i<nValues; ++i)
  {
    sumBup += ((series->XValues->operator [](i) - meanX)
             * (series->YValues->operator [](i) - meanY));
    sumBdown+= ((series->XValues->operator [](i) - meanX)
             *  (series->XValues->operator [](i) - meanX));
  }
  slope = sumBup/sumBdown;
  offset = meanY - (slope*meanX);
}

How to: draw a best fitting line of a ChartSeries?

Using the function getTrendLine above:

void drawTrendLine(TChart * chart,const int& seriesFrom,const int& seriesTo)
{
  double offset, slope;
  const double minX = chart->Series[seriesFrom]->XValues->MinValue;
  const double maxX = chart->Series[seriesFrom]->XValues->MaxValue;
  if (minX!=maxX)
  {
    getTrendLine(chart->Series[seriesFrom],offset,slope);
    chart->Series[seriesTo]->AddXY(minX, offset + (minX * slope));
    chart->Series[seriesTo]->AddXY(maxX, offset + (maxX * slope));
  }
}

Code links

TChart links

TChart is not present in the CLX

Pascal VCL TChart

last edited (November 18, 2006) by bilderbikkel, Number of views: 2595, Current Rev: 5 (Diff)

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