我有一个DataFrame census_df，其中包含美国的县和州的数据。 DataFrame正在起诉嵌套索引，因此第一个索引代表一个州，而第二个索引代表一个县，第三个索引代表一个群体。 DataFrame如下所示。
CENSUS2010POP
STNAME CTYNAME
Alabama Alabama 4779736
Autauga County 54571
Baldwin County 182265
Barbour County 27457
Bibb County 22915
Blount County 57322
Bullock County 10914
Butler County 20947
Calhoun County 118572
Chambers County 34215
Cherokee County 25989
Chilton County 43643
Choctaw County 13859
Clarke County 25833
Clay County 13932
Cleburne County 14972
Coffee County 49948
Colbert County 54428
Conecuh County 13228
Coosa County 11539
Covington County 37765
Crenshaw County 13906
Cullman County 80406
Dale County 50251
Dallas County 43820
DeKalb County 71109
Elmore County 79303
Escambia County 38319
Etowah County 104430
Fayette County 17241
... ...
Wisconsin Washington County 131887
Waukesha County 389891
Waupaca County 52410
Waushara County 24496
Winnebago County 166994
Wood County 74749
Wyoming Wyoming 563626
Albany County 36299
Big Horn County 11668
Campbell County 46133
Carbon County 15885
Converse County 13833
Crook County 7083
Fremont County 40123
Goshen County 13249
Hot Springs County 4812
Johnson County 8569
Laramie County 91738
Lincoln County 18106
Natrona County 75450
Niobrara County 2484
Park County 28205
Platte County 8667
Sheridan County 29116
Sublette County 10247
Sweetwater County 43806
Teton County 21294
Uinta County 21118
Washakie County 8533
Weston County 7208
现在，我想根据population列的值对给定状态的的第二个索引进行排序。我尝试使用
census_df = census_df.sort('CENSUS2010POP')
但是，然后我将所有值排序：
CENSUS2010POP
STNAME CTYNAME
Texas Loving County 82
Hawaii Kalawao County 90
Texas King County 286
Kenedy County 416
Nebraska Arthur County 460
如何根据每个州内的人口对县进行排序？任何帮助都非常感谢。
答案 0 :(得分：1)
我认为您需要STNAME第一级apply，然后CENSUS2010POP功能groupby列STNAME。因此print (census_df.groupby(level=0)['CENSUS2010POP']
.apply(lambda x: x.sort_values())
.reset_index(level=0,drop=True))
STNAME CTYNAME
Alabama Bullock County 10914
Choctaw County 13859
Butler County 20947
Bibb County 22915
Clarke County 25833
Cherokee County 25989
Barbour County 27457
Chambers County 34215
Chilton County 43643
Autauga County 54571
Blount County 57322
Calhoun County 118572
Baldwin County 182265
Alabama 4779736
Wisconsin Waushara County 24496
Waupaca County 52410
Wood County 74749
Washington County 131887
Winnebago County 166994
Waukesha County 389891
Wyoming Crook County 7083
Big Horn County 11668
Goshen County 13249
Converse County 13833
Carbon County 15885
Albany County 36299
Fremont County 40123
Campbell County 46133
Wyoming 563626
Name: CENSUS2010POP, dtype: int64
保持静态，仅按此列的值排序第二级：
{{1}}