// Take a single column and split it into multiple.
internal void CreateColumnFromSplit <T>(Func <Row, T> fpSplit)
where T : IColumnSet, new()
{
T dummy = new T();
string[] fields = dummy.GetFields();
// Allocate new columns
Column[] newColumns = new Column[fields.Length];
for (int i = 0; i < fields.Length; i++)
{
newColumns[i] = new Column(fields[i], this.NumRows);
this.AddColumnLast(newColumns[i]);
}
// Apply splitter function
int rows = this.NumRows;
for (int r = 0; r < rows; r++)
{
Row row = new RowInMemory(this, r);
var result = fpSplit(row);
// Place results into new columns
for (int i = 0; i < fields.Length; i++)
{
newColumns[i].Values[r] = result.GetValue(i);
}
}
}
/// <summary>
/// Only keep rows where the predicate returns true
/// </summary>
/// <param name="predicate">predicate to execute on each row</param>
public void KeepRows(Func <Row, bool> predicate)
{
if (predicate == null)
{
throw new ArgumentNullException("predicate");
}
// Want to avoid multiple memory allocations
List <int> index = new List <int>();
// take a first pass through to evaluate the predicate and track
// which rows to keep
int rows = this.NumRows;
for (int r = 0; r < rows; r++)
{
Row row = new RowInMemory(this, r);
bool keep = predicate(row);
if (keep)
{
index.Add(r);
}
}
int rows2 = index.Count; // new number of rows.
int numColumns = this.Columns.Length;
// Now allocate the new columns lengths
var columns = new Column[numColumns];
for (int i = 0; i < numColumns; i++)
{
columns[i] = new Column(this.Columns[i].Name, rows2);
}
// Copy the the rows we decided to keep.
for (int r = 0; r < rows2; r++)
{
int rOld = index[r];
for (int i = 0; i < numColumns; i++)
{
columns[i].Values[r] = this.Columns[i].Values[rOld];
}
}
this.Columns = columns;
Utility.Assert(this.NumRows == rows2);
}
