如何使用For Loop两次查找数据表列和行？

Question

I want to use for loop to get average of datatable columns and rows. What I want to do is that what if there are 100 ~ 1000 columns and rows, I can't keep on adding them in the code. is there one simple code that can get average of automatically as I add columns and rows?

here is my code, I am stuck I don't know what to write in ?? area below and this code gets me error please help...

private void button1_Click(object sender, EventArgs e)
    {
        DataTable dtGrid = gridData.DataSource as DataTable;
        DataTable dtResult = new DataTable();
        Math columnIndex = new Math();

        List<double> avgList = new List<double>();

        for (int i = 0; i < dtGrid.Columns.Count; i++)
        {

            for (int k = 1; k < dtGrid.Rows.Count; k++)
            {
                // ??
                avgList.Add(Convert.ToDouble(dtGrid.Rows[i].ToString()));
            }

        }
        //this is from other class name Math
        /* public double getAverageValue(List<double> avgList)
        {
            double averageList = 0;

            averageList = MathNet.Numerics.Statistics.Statistics.Mean(avgList.ToList());

            return averageList;
        }*/ 
        double averageX1 = columnIndex.getAverageValue(avgList);

        List<Math> list = new List<Math>();

        //using get; set from other class 
        list.Add(new Math { Result = "Average", X1 = averageX1.ToString() });

        gridData2.DataSource = list;
    }
}

}

Answer 1

It looks like your loop is inside out. Try this:

DataTable dtGrid = gridData.DataSource as DataTable;
DataTable dtResult = new DataTable();
Math columnIndex = new Math();

List<double> avgList = new List<double>();
for (int k = 1; k < dtGrid.Rows.Count; k++)
{
    for (int i = 0; i < dtGrid.Columns.Count; i++)
    {
        // ??
        avgList.Add(Convert.ToDouble(dtGrid.Rows[k].Columns[i].ToString()));
    }
}

This logic averages all columns in a row together. If you need,, you can create a Dictionary and average each column separately. Something like thisL

Dictionary<int, List<double>> AvgColumnList = new Dictionary<int, System.Collections.Generic.List<double>>();

This uses a dictionary that contains a list for each column in the row. If there are 100 columns, then there will be 100 entries in the dictionary with index 0 - 99. Each dictionary item will contain a list of doubles.

for (int k = 1; k < dtGrid.Rows.Count; k++)
{
    for (int i = 0; i < dtGrid.Columns.Count; i++)
    {
        if (!AvgColumnList.Keys.Contains(i))
            AvgColumnList.Add(i, new List<double>());

        AvgColumnList[i].Add(Convert.ToDouble(dtGrid.Rows[k].Columns[i].ToString()));
    }
}

Answer 2

DataTable is zero index based, in your code row count started from 1 it should be 0 , also dtGrid.Rows[i] is a row not the cell value. Use below code to loop through each cell of a DataTable

Update : Code updated as OP want to save each column data separately and irrespective of column numbers.

 List<List<double>> perColumnAvg = new List<List<double>>();

 for (int i = 0; i < dtGrid.Columns.Count; i++)
 {
     avgList = new List<double>();
     for (int k = 0; k < dtGrid.Rows.Count; k++)
     {
         // ??
         avgList.Add(Convert.ToDouble(dtGrid.Rows[k][i].ToString()));
     }
     perColumnAvg.Add(avgList);
 }

Now you can compute individual column average as

foreach (var columnList in perColumnAvg)
{
    // place your logic here.
    columnIndex.getAverageValue(columnList);
}

And can compute avg across table using.

double tableAvg = columnIndex.getAverageValue(perColumnAvg.SelectMany(s=>s));