ph-math/src/main/java/com/helger/numbercruncher/matrix/Matrix.java
public float at (final int r, final int c) throws MatrixException
  {
    if ((r < 0) || (r >= m_nRows) || (c < 0) || (c >= m_nCols))
    {
      throw new MatrixException (MatrixException.INVALID_INDEX);
    }

    return m_aValues[r][c];
  }
public float at (final int r, final int c) throws MatrixException
  {
    if ((r < 0) || (r >= m_nRows) || (c < 0) || (c >= m_nCols))
    {
      throw new MatrixException (MatrixException.INVALID_INDEX);
    }

    return m_aValues[r][c];
  }
Get the value of element [r,c] in the matrix.

@param r
the row index
@param c
the column index
@return the value
@throws MatrixException
for an invalid index