我在r中有一个df，如下所示：
# A tibble: 70 x 2
value Month_considered
dbl> <S3: yearmon>
24.8 Apr 2017
47.0 Apr 2017
35.2 Apr 2017
19.4 Apr 2017
30.9 Apr 2017
6.64 Apr 2017
10.7 Apr 2017
11.5 May 2017
36.3 May 2017
6.74 May 2017
# ... with 60 more rows
因此，当我执行levels(intrc_flow$Month_considered)或unique(intrc_flow$Month_considered)时，得到的输出如下：
[1] Apr-17 May-17 Jun-17 Jul-17 Aug-17 Sep-17 Oct-17 Nov-17 Dec-17 Jan-18 Feb-18
12 Levels: Apr-17 Aug-17 Dec-17 Feb-18 Jan-18 Jul-17 Jun-17 Mar-17 ... Sep-17
如何将级别输出为Apr 2017而不是Apr-17。谢谢。