[1] 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101
[14] 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101 19980101
[27] 19980101 19980101 20151114 20151114 20151114 20151114 20151114 20151114 20151114 20151114 20151114 20151114 20151114
[40] 20151114 20151114 20151114 20151121 20151121 20151121 20151121 20151121 20151121 20151121 20151121 20151121 20151121
[53] 20151121 20151121 20151121 20151121
我的CDATE是这样一串日期，我想选取<20160501的最大的那个数所在的位置，但是我用which(max(CDATE<=20160501))
出来的结果却是这样
Error in which(max(CDATE <= startdate)) :
  argument to 'which' is not logical
请问如何选取小于某个数的最大值