create_coordinates      Function to create coordinates for a Hilbert
                        Curve This functions adds three columns to a
                        data frame: reld, x, y
create_id_column        Function to create an id column from a
                        character column
d2xy                    Returns the x/y-position for a distance d in n
                        possible values
d2xy2                   Returns the x/y-position for a Vector of
                        distances d in n possible values
gghilbertplot           Function to create the Hilbert Plot
hilbertd2xy             Hilbert conversion, distance to coordinates
order4                  Finds the order of the next highest number to
                        the power of 4
