June 2020
Beginner to intermediate
522 pages
9h 6m
Chinese
Content preview from R 语言经典实例（原书第 2 版）
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d <- as.Date("2020-04-02")
as.POSIXlt(d)$wday
#> [1] 4
as.POSIXlt(d)$yday
#> [1] 92
一个常见的错误是未能在返回的年份加上 1900，该错误使你误以为生活在很久以前：
as.POSIXlt(d)$year # Oops!
#> [1] 120
as.POSIXlt(d)$year + 1900
#> [1] 2020
7.13 创建日期序列
7.13.1 问题
你想要创建一个日期序列，例如日、月份或年度的日期序列。
7.13.2 解决方案
seq 函数是一个泛型函数，具有一个 Date 对象的版本。它可以创建一个 Date 序列，
类似于它创建一个数字序列的方式。
7.13.3 讨论
seq 的典型用法指定开始日期（from）、结束日期（to）和增量（ by）。增量 1 表示每
日日期：
s <- as.Date("2019-01-01")
e <- as.Date("2019-02-01")
seq(from = s, to = e, by = 1) # One month of dates
#> [1] "2019-01-01" "2019-01-02" "2019-01-03" "2019-01-04" "2019-01-05"
#> [6] "2019-01-06" "2019-01-07" "2019-01-08" "2019-01-09" "2019-01-10"
#> [11] "2019-01-11" "2019-01-12" ...
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