def read_er_ages_file(self, path, ignore_lines_n, sort_by_these_names):
        '''
        read er_ages, sort it by site or sample (the header that is not empty)
        and convert ages to calendar year

        '''
        DATA = {}
        fin = open(path, 'r')
        # ignore first lines
        for i in range(ignore_lines_n):
            fin.readline()
        # header
        line = fin.readline()
        header = line.strip('\n').split('\t')
        # print header
        for line in fin.readlines():
            if line[0] == "#":
                continue
            tmp_data = {}
            tmp_line = line.strip('\n').split('\t')
            for i in range(len(tmp_line)):
                if i >= len(header):
                    continue
                tmp_data[header[i]] = tmp_line[i]
            for name in sort_by_these_names:
                if name in list(tmp_data.keys()) and tmp_data[name] != "":
                    er_ages_rec = self.convert_ages_to_calendar_year(tmp_data)
                    DATA[tmp_data[name]] = er_ages_rec
        fin.close()
        return(DATA)