在R中的两个月之间插入月日期

在R中有两个日期，我想在它们之间创建一个日期向量，间隔一个月。然而，R似乎使用了31天的间隔（有时？）。例如：

x <- as.Date("31-01-1900", "%d-%m-%Y")
y <- as.Date("31-01-1901", "%d-%m-%Y")
seq(x, y, by="month")

 [1] "1900-01-31" "1900-03-03" "1900-03-31" "1900-05-01" "1900-05-31"
 [6] "1900-07-01" "1900-07-31" "1900-08-31" "1900-10-01" "1900-10-31"
[11] "1900-12-01" "1900-12-31" "1901-01-31"

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R知道月份的长度吗，还是我必须手工完成？

我们可以使用

lubridate

library(lubridate)
x <- as.Date("31-01-1900", "%d-%m-%Y")
y <- as.Date("31-01-1901", "%d-%m-%Y")
c(x, x %m+% months(1:11), y)

[1] "1900-01-31" "1900-02-28" "1900-03-31" "1900-04-30"
[5] "1900-05-31" "1900-06-30" "1900-07-31" "1900-08-31"
[9] "1900-09-30" "1900-10-31" "1900-11-30" "1900-12-31"
[13] "1901-01-31"

---

您可以生成每个月第一个的序列，然后减去1

seq(as.Date("1900-02-01"), length = 12, by="1 month") - 1
# [1] "1900-01-31" "1900-02-28" "1900-03-31" "1900-04-30" "1900-05-31" "1900-06-30"
# [7] "1900-07-31" "1900-08-31" "1900-09-30" "1900-10-31" "1900-11-30" "1900-12-31"

## the same can be achieved with `seq.Date()`
# seq.Date(as.Date("1900-02-01"), by = "1 month", length.out = 12) - 1 

---

您可以查看lubridate的

package，不过这是？seq.POSIXt的一段摘录：“使用“month”首先提前月份，而不更改日期：如果这导致一个月中的某一天无效，则将其向前计算到下一个月。”因此，这些函数中的这一点看起来是固定的。这两个答案都非常好，但我更喜欢这个，因为它不需要包装；我通常会先尝试一个基本的解决方案。
lubridate::add_with_rollback(x, months(0:12))

 [1] "1900-01-31" "1900-02-28" "1900-03-31" "1900-04-30"
 [5] "1900-05-31" "1900-06-30" "1900-07-31" "1900-08-31"
 [9] "1900-09-30" "1900-10-31" "1900-11-30" "1900-12-31"
[13] "1901-01-31"

seq(as.Date("1900-02-01"), length = 12, by="1 month") - 1
# [1] "1900-01-31" "1900-02-28" "1900-03-31" "1900-04-30" "1900-05-31" "1900-06-30"
# [7] "1900-07-31" "1900-08-31" "1900-09-30" "1900-10-31" "1900-11-30" "1900-12-31"

## the same can be achieved with `seq.Date()`
# seq.Date(as.Date("1900-02-01"), by = "1 month", length.out = 12) - 1