/// <summary>
/// Create a view of a parent matrix with a subset of the rows (perhaps in a different order) and
/// a subset of the cols (perhaps in a different order). If the subsets happen to include all
/// rows and cols in the same order, the parent matrix is returned.
/// This is a 'view' in the sense that changes to the values in either matrix will be reflected in both.
/// </summary>
/// <typeparam name="TRowKey">The type of the row key. Usually "String"</typeparam>
/// <typeparam name="TColKey">The type of the col key. Usually "String"</typeparam>
/// <typeparam name="TValue">The type of the value, for example, double, int, char, etc.</typeparam>
/// <param name="parentMatrix">The matrix to wrap.</param>
/// <param name="rowKeySequence">A sequence of rowKeys that specifies the subset of rows to include and their desired order.</param>
/// <param name="colKeySequence">A sequence of colKeys that specifies the subset of cols to include and their desired order.</param>
/// <returns>A matrix with the desired rows and cols in their desired order.</returns>
static public Matrix<TRowKey, TColKey, TValue> SelectRowsAndColsView<TRowKey, TColKey, TValue>(this Matrix<TRowKey, TColKey, TValue> parentMatrix, IEnumerable<TRowKey> rowKeySequence, IEnumerable<TColKey> colKeySequence)
{
//If the new won't change anything, just return the parent
if (parentMatrix.RowKeys.SequenceEqual(rowKeySequence) && parentMatrix.ColKeys.SequenceEqual(colKeySequence))
{
return parentMatrix;
}
//!!!Could check of this is a SelectRowsAndColsView of a SelectRowsAndColsView and simplify (see TransposeView for an example)
var matrixView = new SelectRowsAndColsView<TRowKey, TColKey, TValue>();
matrixView.SetUp(parentMatrix, rowKeySequence, colKeySequence);
return matrixView;
}
private static DenseMatrix <TRowKey, TColKey, TValue> MaterializeSelectRowsColsViewToDenseMatrix <TRowKey, TColKey, TValue>(SelectRowsAndColsView <TRowKey, TColKey, TValue> selectRowsAndColsView)
{
DenseMatrix <TRowKey, TColKey, TValue> parent = (DenseMatrix <TRowKey, TColKey, TValue>)selectRowsAndColsView.ParentMatrix;
var matrix = new DenseMatrix <TRowKey, TColKey, TValue>();
matrix._rowKeys = selectRowsAndColsView.RowKeys;
matrix._colKeys = selectRowsAndColsView.ColKeys;
matrix._indexOfRowKey = selectRowsAndColsView.IndexOfRowKey;
matrix._indexOfColKey = selectRowsAndColsView.IndexOfColKey;
matrix._missingValue = parent.MissingValue;
matrix.ValueArray = new TValue[matrix.RowCount, matrix.ColCount];
IList <int> oldRowIndexList = selectRowsAndColsView.IndexOfParentRowKey;
IList <int> oldColIndexList = selectRowsAndColsView.IndexOfParentColKey;
for (int newRowIndex = 0; newRowIndex < matrix.RowCount; ++newRowIndex)
{
int oldRowIndex = oldRowIndexList[newRowIndex];
for (int newColIndex = 0; newColIndex < matrix.ColCount; ++newColIndex)
{
matrix.ValueArray[newRowIndex, newColIndex] = parent.ValueArray[oldRowIndex, oldColIndexList[newColIndex]];
}
}
return(matrix);
}
