部分数据如下,我需要将数据按照年份和Size排序,请问如何对每年的样本选取Size的前33%和后33%,并且对前33%的样本生成新变量FC=0,对后33%的样本生成新变量FC=1?求各位指点
code size year
2 11.680522 2013
2 11.706213 2014
2 11.786251 2015
2 11.919431 2016
2 12.066455 2017
2 12.184288 2018
2 12.238028 2019
4 8.3840882 2013
4 8.5292796 2014
4 8.6006174 2015
4 8.3496976 2016
4 8.4295008 2017
4 8.5455266 2018
4 9.1744931 2019
5 9.0750554 2013
5 9.1356617 2014
5 9.3412384 2015
5 9.4026457 2016
5 9.4642063 2017
5 9.4943527 2018
5 9.4817064 2019
8 8.7970084 2013
8 8.828678 2014
8 9.5550164 2015
8 9.9134248 2016
8 10.028503 2017
8 10.019796 2018
8 10.08079 2019
9 10.133916 2013
9 10.16807 2014
9 10.258013 2015
9 10.334914 2016
9 10.433121 2017
9 10.474941 2018
9 10.480148 2019


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