R datesequence 获取特定日期的索引

Question

我有一个按日频率排列的日期序列。现在我需要每个月的第一天和每个月的最后一天的索引。我不知道如何实现这一点。

# Just a simple datesequence
dateSeq <- seq(from=as.Date("2013-01-01"), to=as.Date("2017-01-01"), by="day")

我需要一个包含当月第一天 (1, 32,...) 和当月最后一天 (31, 68,...) 的所有索引的向量

编辑：我还需要一周、一年、学期、两个月半年的第一天和最后一天，所以应该有一个一致的方法

例如，如果日期序列在 2017 年 3 月 12 日结束，我不需要这一天在索引中，因为它不是月的最后一天，而是序列中月的最后一天。

Answer 1

这里是月份的第一天和最后一天以及工作日的索引

库（润滑）

b=unique(floor_date(dateSeq, "month"))
> match(b,dateSeq)
 [1]    1   32   60   91  121  152  182  213  244  274  305  335  366  397  425  456  486  517  547  578  609  639  670  700  731  762  790  821  851  882  912  943
[33]  974 1004 1035 1065 1096 1127 1156 1187 1217 1248 1278 1309 1340 1370 1401 1431 1462

> c=unique(floor_date(dateSeq, "month"))-1
> match(c,dateSeq)
 [1]   NA   31   59   90  120  151  181  212  243  273  304  334  365  396  424  455  485  516  546  577  608  638  669  699  730  761  789  820  850  881  911  942
[33]  973 1003 1034 1064 1095 1126 1155 1186 1216 1247 1277 1308 1339 1369 1400 1430 1461

每月的第一天工作日

> unique(floor_date(dateSeq, "month"))
 [1] "2013-01-01" "2013-02-01" "2013-03-01" "2013-04-01" "2013-05-01" "2013-06-01" "2013-07-01" "2013-08-01" "2013-09-01" "2013-10-01" "2013-11-01" "2013-12-01"
[13] "2014-01-01" "2014-02-01" "2014-03-01" "2014-04-01" "2014-05-01" "2014-06-01" "2014-07-01" "2014-08-01" "2014-09-01" "2014-10-01" "2014-11-01" "2014-12-01"
[25] "2015-01-01" "2015-02-01" "2015-03-01" "2015-04-01" "2015-05-01" "2015-06-01" "2015-07-01" "2015-08-01" "2015-09-01" "2015-10-01" "2015-11-01" "2015-12-01"
[37] "2016-01-01" "2016-02-01" "2016-03-01" "2016-04-01" "2016-05-01" "2016-06-01" "2016-07-01" "2016-08-01" "2016-09-01" "2016-10-01" "2016-11-01" "2016-12-01"
[49] "2017-01-01"
> wday(unique(floor_date(dateSeq, "month")))
 [1] 3 6 6 2 4 7 2 5 1 3 6 1 4 7 7 3 5 1 3 6 2 4 7 2 5 1 1 4 6 2 4 7 3 5 1 3 6 2 3 6 1 4 6 2 5 7 3 5 1
> weekdays(unique(floor_date(dateSeq, "month")))
 [1] "Tuesday"   "Friday"    "Friday"    "Monday"    "Wednesday" "Saturday"  "Monday"    "Thursday"  "Sunday"    "Tuesday"   "Friday"    "Sunday"    "Wednesday"
[14] "Saturday"  "Saturday"  "Tuesday"   "Thursday"  "Sunday"    "Tuesday"   "Friday"    "Monday"    "Wednesday" "Saturday"  "Monday"    "Thursday"  "Sunday"   
[27] "Sunday"    "Wednesday" "Friday"    "Monday"    "Wednesday" "Saturday"  "Tuesday"   "Thursday"  "Sunday"    "Tuesday"   "Friday"    "Monday"    "Tuesday"  
[40] "Friday"    "Sunday"    "Wednesday" "Friday"    "Monday"    "Thursday"  "Saturday"  "Tuesday"   "Thursday"  "Sunday" 

工作日的最后一天

> unique(floor_date(dateSeq, "month"))-1
 [1] "2012-12-31" "2013-01-31" "2013-02-28" "2013-03-31" "2013-04-30" "2013-05-31" "2013-06-30" "2013-07-31" "2013-08-31" "2013-09-30" "2013-10-31" "2013-11-30"
[13] "2013-12-31" "2014-01-31" "2014-02-28" "2014-03-31" "2014-04-30" "2014-05-31" "2014-06-30" "2014-07-31" "2014-08-31" "2014-09-30" "2014-10-31" "2014-11-30"
[25] "2014-12-31" "2015-01-31" "2015-02-28" "2015-03-31" "2015-04-30" "2015-05-31" "2015-06-30" "2015-07-31" "2015-08-31" "2015-09-30" "2015-10-31" "2015-11-30"
[37] "2015-12-31" "2016-01-31" "2016-02-29" "2016-03-31" "2016-04-30" "2016-05-31" "2016-06-30" "2016-07-31" "2016-08-31" "2016-09-30" "2016-10-31" "2016-11-30"
[49] "2016-12-31"
> wday(unique(floor_date(dateSeq, "month"))-1)
 [1] 2 5 5 1 3 6 1 4 7 2 5 7 3 6 6 2 4 7 2 5 1 3 6 1 4 7 7 3 5 1 3 6 2 4 7 2 5 1 2 5 7 3 5 1 4 6 2 4 7
> weekdays(unique(floor_date(dateSeq, "month"))-1)
 [1] "Monday"    "Thursday"  "Thursday"  "Sunday"    "Tuesday"   "Friday"    "Sunday"    "Wednesday" "Saturday"  "Monday"    "Thursday"  "Saturday"  "Tuesday"  
[14] "Friday"    "Friday"    "Monday"    "Wednesday" "Saturday"  "Monday"    "Thursday"  "Sunday"    "Tuesday"   "Friday"    "Sunday"    "Wednesday" "Saturday" 
[27] "Saturday"  "Tuesday"   "Thursday"  "Sunday"    "Tuesday"   "Friday"    "Monday"    "Wednesday" "Saturday"  "Monday"    "Thursday"  "Sunday"    "Monday"   
[40] "Thursday"  "Saturday"  "Tuesday"   "Thursday"  "Sunday"    "Wednesday" "Friday"    "Monday"    "Wednesday" "Saturday"