public double at(int r, int c) throws MatrixException
    {
        if ((r < 0) || (r >= nRows) || (c < 0) || (c >= nCols)) {
            throw new MatrixException(MatrixException.INVALID_INDEX);
        }

        return values[r][c];
    }
public double at ( int r , int c ) throws MatrixException { if ( ( r < 0 ) || ( r >= nRows ) || ( c < 0 ) || ( c >= nCols ) ) { throw new MatrixException ( MatrixException . INVALID_INDEX ) ; } return values [ 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 numbercruncher.MatrixException for an invalid index