public Matrix Adj()
{
var rowIndices = RowIndices.OrderBy(index => index).ToList();
var columnIndices = ColumnIndices.OrderBy(index => index).ToList();
if (rowIndices.Count == 1)
{
return(Identity().Transpose());
}
var adj = new Matrix(
columnIndices,
rowIndices);
// Calculate cofactors.
for (var rowIndexIndex = 0; rowIndexIndex < rowIndices.Count; ++rowIndexIndex)
{
for (var columnIndexIndex = 0; columnIndexIndex < columnIndices.Count; ++columnIndexIndex)
{
var rowIndex = rowIndices[rowIndexIndex];
var columnIndex = columnIndices[columnIndexIndex];
var minorRowIndices = rowIndices.Where(index => index != rowIndex).ToList();
var minorColumnIndices = columnIndices.Where(index => index != columnIndex).ToList();
var cofactorValue = Det(
minorRowIndices,
minorColumnIndices);
adj._elements[columnIndex][rowIndex] = (rowIndexIndex + columnIndexIndex) % 2 == 0 ?
cofactorValue : -cofactorValue;
}
}
return(adj);
}
public IDataFrame GetSubsetByRows(IList <int> rowIndices, bool useRowNames = false)
{
var newTable = new DataTable();
foreach (DataColumn col in DataTable.Columns)
{
newTable.Columns.Add(new DataColumn(col.ColumnName, col.DataType));
}
rowIndices = useRowNames ? RowNamesToRowIndices(rowIndices) : rowIndices;
foreach (var rowIdx in rowIndices)
{
newTable.Rows.Add(DataTable.Rows[rowIdx].ItemArray);
}
return(new DataFrame(newTable, RowIndices.Where((rowName, rowIdx) => rowIndices.Contains(rowIdx)).ToList()));
}
public override double[] GetRows()
{
return(RowIndices.Select(i => rows[i - 1]).ToArray()); // get aligned rows
}
public Fraction Det()
{
return(Det(
RowIndices.OrderBy(index => index).ToList(),
ColumnIndices.OrderBy(index => index).ToList()));
}
private int RowNameToIndex(int rowName)
{
return(RowIndices.IndexOf(rowName));
}