/// <summary>
/// Writes the matrix to a file in sparse format. A directory will be created if needed.
/// The first line is "var" TAB "cid" TAB "val"
/// Next is one line per nonmissing value. Each line is: rowKey TAB colKey TAB value
/// </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="matrix">The matrix to write</param>
/// <param name="filename">The filename to write to.</param>
public static void WriteSparse <TRowKey, TColKey, TValue>(this Matrix <TRowKey, TColKey, TValue> matrix, string filename)
{
FileUtils.CreateDirectoryForFileIfNeeded(filename);
using (TextWriter writer = File.CreateText(filename))
{
matrix.WriteSparse(writer);
}
}
