const double h = 0.001;

void finite_derivative()
{
	WorksheetPage wpg;
	wpg.Create("Origin");
	Worksheet wks = wpg.Layers(0);
	while( wks.DeleteCol(0) );
	wks.AddCol();
	wks.Columns(0).SetType(OKDATAOBJ_DESIGNATION_X);
	wks.AddCol();
	wks.Columns(1).SetLabel("Function");
	wks.AddCol();
	wks.Columns(2).SetLabel("Derivative");
	

	Dataset dsX(wks, 0);
	Dataset dsY(wks, 1);
	Dataset dsDY(wks, 2);
	
	for(double x = 0; x < 10; x += 0.1)
	{
		dsX.Add(x);
		dsY.Add(myfunc(x));
		dsDY.Add(myderiv(x));
	}	
	
	GraphPage gpg;
	gpg.Create("Origin");
	GraphLayer gly = gpg.Layers(0);
	gly.AddPlot(wks);
	gly.LT_execute("legend;");
	gly.Rescale();
}

static double myfunc(double x)
{
	return sin(x + 2.5);
}

static double myderiv(double x)
{
	return ( (myfunc(x+h) - myfunc(x-h)) / (2 * h) )
}