加入我有如下数据:
dates 0
numbers letters
0 a 2013-01-01 0.261092
2013-01-02 -1.267770
2013-01-03 0.008230
b 2013-01-01 -1.515866
2013-01-02 0.351942
2013-01-03 -0.245463
c 2013-01-01 -0.253103
2013-01-02 -0.385411
2013-01-03 -1.740821
1 a 2013-01-01 -0.108325
2013-01-02 -0.212350
2013-01-03 0.021097
b 2013-01-01 -1.922214
2013-01-02 -1.769003
2013-01-03 -0.594216
c 2013-01-01 -0.419775
2013-01-02 1.511700
2013-01-03 0.994332
2 a 2013-01-01 -0.020299
2013-01-02 -0.749474
2013-01-03 -1.478558
b 2013-01-01 -1.357671
2013-01-02 0.161185
2013-01-03 -0.658246
c 2013-01-01 -0.564796
2013-01-02 -0.333106
2013-01-03 -2.814611
我想要选择(0, 'b')和(1, 'c')的数据构建一个新的dataframe,请问怎么实现?