从数据表创建数据透视表

Question

我正在使用 C# winforms 创建一个需要将数据表转换为数据透视表的应用程序。我的数据透视表从 SQL 端工作正常，但从数据表创建它似乎更棘手。我似乎找不到任何内置在.NET中的东西。

注意：我必须从 .NET 端执行此操作，因为我在创建数据透视之前操作数据。

我已经阅读了一些与此类似的文章，但我很难将它们应用于我的问题。

*我有一个包含“StartDateTime”、“Tap”和“Data”列的数据表。应将开始日期分组在一起并对数据值进行平均（有时每个开始日期不止一个数据值）。下表如下：

数据透视表的输出应如下图所示（但不是四舍五入的值）。列号是不同的抽头号（每个唯一的抽头号一个）。

如何从数据表创建此数据透视表？

编辑：忘了提一下，这些抽头值并不总是从 1 到 4，它们的数量和值确实不同。

Answer 1

学习哈希轴手筋：

var inDT = new DataTable();
// Fill the input table

var oDT = new DataTable();
var dfq = new Dictionary<DateTime, DataRow>;
oDT.Columns.Add("StartDateTime", typeof(DateTime));
for (int i = 0; i < inDT.Rows.Count; i++) {
    var key = (DateTime)inDT.Rows[i][0];
    var row = (String)inDT.Rows[i][2];
    var data = (Double)inDT.Rows[i][1];

    if (!oDT.Columns.Contains(row)) {
       oDT.Columns.Add(row);
    }
    if (dfq.ContainsKey(key)) {
        dfq[key][row] = data;
    } else {
        var oRow = oDT.NewRow();
        oRow[0] = key;
        oRow[row] = data;
        dfq.Add(key, oRow);
        oDT.Rows.Add(oRow);
    }
}
// pivot table in oDT

Answer 2

另外一小段代码可以旋转您想要的任何表格：

        var dataTable = new DataTable(); // your input DataTable here!
        var pivotedDataTable = new DataTable(); //the pivoted result
        var firstColumnName = "Year";
        var pivotColumnName = "Codes";

        pivotedDataTable.Columns.Add(firstColumnName);

        pivotedDataTable.Columns.AddRange(
            dataTable.Rows.Cast<DataRow>().Select(x => new DataColumn(x[pivotColumnName].ToString())).ToArray());

        for (var index = 1; index < dataTable.Columns.Count; index++)
        {
            pivotedDataTable.Rows.Add(
                new List<object> { dataTable.Columns[index].ColumnName }.Concat(
                    dataTable.Rows.Cast<DataRow>().Select(x => x[dataTable.Columns[index].ColumnName])).ToArray());
        }

Answer 3

可以使用免费的NReco.PivotData 聚合库轻松计算这样的数据透视表：

DataTable t;  // assume it has: StartDateTime, Data, Tap
var pivotData = new PivotData(
    new string[] {"StartDateTime","Tap"},
    new AverageAggregatorFactory("Data"),
    new DataTableReader(t) );
var pvtTbl = new PivotTable(
    new [] {"StartDateTime"},  // row dimension(s)
    new [] {"Tap"}, // column dimension(s),
    pivotData);

行和列键由 pvtTbl.RowKeys 和 pvtTbl.ColumnKeys 集合表示；值/总计可以通过索引器（例如：pvtTbl[0,0].Value）或行+列键（例如：pivotData[new Key(new DateTime(2012, 3, 30, 11, 42, 00)), new Key(4)].Value）访问。

Answer 4

也许这会对你有所帮助。它在 vb.net 中。

Public Function pivot_datatable(ByVal datatable_source As DataTable, ByVal datacolumn_rows As DataColumn(), ByVal datacolumn_columns As DataColumn, ByVal datacolumn_value As DataColumn) As DataTable
    Dim temp_datacolumn As DataColumn
    Dim current_datarow As DataRow
    Dim datarow_destination As DataRow = Nothing
    Dim current_column_name As String = ""
    Dim primary_key() As DataColumn = New DataColumn() {}
    Dim key_columns() As Object
    Dim newOrdinal As Integer
    Dim i As Integer
    Dim sort_string As String = ""

    Try
        pivot_datatable = New DataTable()

        For Each temp_datacolumn In datatable_source.Columns
            If temp_datacolumn.Ordinal <> datacolumn_columns.Ordinal AndAlso temp_datacolumn.Ordinal <> datacolumn_value.Ordinal Then
                array_insert(primary_key, pivot_datatable.Columns.Add(temp_datacolumn.ColumnName, temp_datacolumn.DataType))
                sort_string &= temp_datacolumn.ColumnName & " ASC, "
            End If
        Next
        pivot_datatable.PrimaryKey = primary_key

        For Each current_datarow In datatable_source.Rows ' Main Process to add values to pivot table
            current_column_name = current_datarow(datacolumn_columns.Ordinal).ToString
            If Not pivot_datatable.Columns.Contains(current_column_name) Then ' Column is new
                temp_datacolumn = pivot_datatable.Columns.Add(current_column_name, datacolumn_value.DataType)
                newOrdinal = temp_datacolumn.Ordinal
                For i = newOrdinal - 1 To datatable_source.Columns.Count - 2 Step -1
                    If temp_datacolumn.ColumnName.CompareTo(pivot_datatable.Columns(i).ColumnName) < 0 Then
                        newOrdinal = i
                    End If
                Next
                temp_datacolumn.SetOrdinal(newOrdinal)
            End If

            key_columns = New Object() {}
            For Each data_column As DataColumn In datacolumn_rows
                array_insert(key_columns, current_datarow(data_column.Ordinal).ToString)
            Next data_column
            datarow_destination = pivot_datatable.Rows.Find(key_columns)
            If datarow_destination Is Nothing Then ' New Row
                datarow_destination = pivot_datatable.NewRow()
                For Each temp_datacolumn In datatable_source.Columns
                    If temp_datacolumn.Ordinal <> datacolumn_columns.Ordinal AndAlso temp_datacolumn.Ordinal <> datacolumn_value.Ordinal Then
                        datarow_destination(temp_datacolumn.ColumnName) = current_datarow(temp_datacolumn.ColumnName)
                    End If
                Next
                pivot_datatable.Rows.Add(datarow_destination)
            End If
            datarow_destination(current_column_name) = current_datarow(datacolumn_value.Ordinal)
        Next

        Return sort_datatable(pivot_datatable, sort_string.Substring(0, sort_string.Length - 2))
    Catch ex As Exception
        Return Nothing
    End Try
End Function