void sum_all_groups(int nGroupCol = 0, int nDataCol = 1)
{
	Worksheet wks = Project.ActiveLayer();
	Dataset dGroup(wks, nGroupCol);
	vector<ushort> vRowMap;
	vRowMap = dGroup;
	Worksheet wResult;
	wResult.Create();
	wResult.AddCol();
	wResult.AddCol();
	wResult.Columns(1).SetName("Mean");
	wResult.Columns(2).SetName("SD");
	wResult.Columns(3).SetName("N");
	wResult.Columns(2).SetType(OKDATAOBJ_DESIGNATION_ERROR);
	BasicStats bsStat;
	Data_sum(&dGroup,&bsStat);
	int iMin = bsStat.min;
	int iMax = bsStat.max;
	int nGroup;
	for(int i=iMin;i<=iMax;i++)
	{
		if( sum_one_group(wks, bsStat, vRowMap, i, nDataCol) )
		{
			wResult.SetCell(nGroup,0,i);
			wResult.SetCell(nGroup,1,bsStat.mean);
			wResult.SetCell(nGroup,2,bsStat.sd);
			wResult.SetCell(nGroup,3,bsStat.N);
			nGroup++;
		}
	}
}
	
int sum_one_group(Worksheet wks, BasicStats &bsStat, vector<ushort> vRowMap, int nGroupVal, int nDataCol)
{
	vector vResult;
	if( wks.ExtractOneGroup(vResult, nDataCol, vRowMap, 0, 0, vRowMap.GetSize()-1, nGroupVal) )
	{
		Dataset dOut;
		dOut.Create(vResult.GetSize());
		dOut = vResult;
		Data_sum(&dOut,&bsStat);
		return bsStat.N;
	}
	return 0;
}

http://www.originlab.com/forum/topic.asp?TOPIC_ID=2924

// %1 : input x dataset
// %2 : input y dataset
// %3 : output x dataset
// %4 : output mean y dataset
// %5 : output sd dataset

def GenMeanSEXY {
MeanYZero=0/0;
MeanYTop=0/0;
MeanYBot=0/0;
sum(%1);
Numpoints=sum.n;
MaxXValue=sum.max;
sum(%2);
MaxYValue=sum.max;
MinYValue=sum.min;
NumdiffX=1; XStart1=1; XFinish1=1; %3[1]=%1[1];
loop(NumXValue,2,NumPoints) {
  If(%1[NumXValue]>%1[XFinish$(NumDiffX)]) {
    NumDiffX=NumDiffX+1;
    XStart$(NumDiffX)=NumXValue;
    %3[NumDiffX]=%1[NumXValue];
  };
  XFinish$(NumDiffX)=NumXValue;
};
loop(NumXValue,1,NumDiffX) {
  NumYValues=XFinish$(NumXValue)-XStart$(NumXValue)+1;
  Create TempY -n NumYValues;
  Copy -b XStart$(NumXValue) %2 TempY -b 1 -e NumYValues;
  Sum(TempY);
  delete -s TempY;
  %4[NumXValue]=sum.mean;
  %5[NumXValue]=sum.sd;
};
MeanYTop=%4[NumDiffX];
If(%3[1]==0) {
  MeanYZero=%4[1];
  MeanYBot=%4[2];
  MinXValue=%3[2];
} else {
  MeanYBot=%4[1];
  MinXValue=%3[1];
};
};