def clean_distance_data(csv_data):
    """Remove redundant column, use location numbers instead of names,
    and convert distance data (a mix of integer and string) to floats.
    """
    for row_index, row in enumerate(csv_data):
        del row[1]
        for col_index, datum in enumerate(row):
            if row_index != 0 and col_index != 0:
                if datum != '':
                    csv_data[row_index][col_index] = float(datum)
        if row_index != 0:
            row[0] = row_index
    for col_index, _ in enumerate(csv_data[0]):
        if col_index != 0:
            csv_data[0][col_index] = col_index
