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SortCols


Unit:SDL_datatable
Class: TDataTable
Declaration: procedure SortCols (SortRowIx: integer; Ascending: boolean; LowCol, LowRow, HighCol, HighRow: integer; IncludeHeaders: boolean);

The method SortCols provides a means to sort the columns of the data table, or part of it, according to the values in a single row. This row is specified by the parameter SortRowIx. The table is sorted column by column within the range [LowCol,LowRow] to [HighCol,HighRow]. The values outside this range are not affected (except for the row addressed by SortRowIx ). The sorting order is determined by the row SortRowIdx which is also sorted within the range [LowCol, HighCol ]. The parameter Ascending specifies whether the valus are to be sorted in ascending (TRUE) or descending (FALSE) order. The parameter IncludeHeaders determines whether the column names, decimal places, and columns attributes are sorted too. Note that in most cases this parameter should be set TRUE.

MATCSORT.gif

The sorting is performed by a modified bubble sort (CombSort), which has been reported to be comparable in speed to QuickSort (see also R.Box, S. Lacey, BYTE magazine, April 1991). The event OnSortExchange is triggered whenever two columns have to be exchanged during the sorting process.

Hint 1: The values of the row SortRowIx are always sorted, even if this row is outside the specified sort range [LowRow, HighRow].

Hint 2: Setting both the low and high parameter of a dimension (i.e. LowCol and HighCol) to zero values forces the method to use all elements of that dimension.

Hint 3: If the sorting criterion is an ordinal or nominal variable the ordinal numbers of the data are used for the sorting process.

Example: The statement MyDTable.SortCols (3, true, 1, 1, MyDTable.NrOfColumns, MyDTable.NrOfRows, true) sorts the whole matrix MyDTable according to the values in Row 3.


Last Update: 2012-Oct-20