我用13版本stata研究评分对票房的影响，所以我把评分等级分成4份。

. egen raveragek=cut(raverage),group(4) label
(584086 missing values generated)

.
. tabulate raveragek

raveragek | Freq. Percent Cum.
------------+-----------------------------------
0- | 13,534 23.95 23.95
6.2- | 14,444 25.56 49.52
7.1- | 14,018 24.81 74.33
7.8- | 14,507 25.67 100.00
------------+-----------------------------------
Total | 56,503 100.00

.
. gen raverage_low=raverage if (raverage<=6.2)
(625824 missing values generated)

.
. gen raverage_mid=raverage if (raverage>6.2)&(raverage<=7.1)
(625615 missing values generated)

.
. gen raverage_upper=raverage if (raverage>7.1)&(raverage<=7.8)
(628332 missing values generated)

.
. gen raverage_up=raverage if (raverage>7.8)&(raverage<=10)
(626087 missing values generated)

然后我把放在panel data里

tsset title_numeric week
panel variable: title_numeric (strongly balanced)
time variable: week, 2 to 56
delta: 1 unit

然而我发现当我运行panel 命令时

xtreg Total_BO raverage_low raverage_mid raverage_upper raverage_up, fe robust

出现提醒 no observations. when i track the problem it shows too many variables specified.

super thanks someone can help me