【862】as.Date in R programming

ref: R语言——日期时间处理

ref: as.Date: Date Conversion Functions to and from Character

ref: Date Formats in R

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as.Date()it can change a normal string into a date format.

format()It can extract the specific date format from a date string.

Example:

> d = "2020-02-21"
> format(as.Date(d), format="%B, %Y")
[1] "February, 2020"
> format(as.Date(d), format="%d %B, %Y")
[1] "21 February, 2020"
> format(as.Date(d), format="%d %B, %Y, %A")
[1] "21 February, 2020, Friday"

Date Formats

Conversion specification	Description	Example
%a	Abbreviated weekday	Sun, Thu
%A	Full weekday	Sunday, Thursday
%b or %h	Abbreviated month	May, Jul
%B	Full month	May, July
%d	Day of the month 01-31	27, 07
%j	Day of the year 001-366	148, 188
%m	Month 01-12	05, 07
%U	Week 01-53 with Sunday as first day of the week	22, 27
%w	Weekday 0-6 Sunday is 0	0, 4
%W	Week 00-53 with Monday as first day of the week	21, 27
%x	Date, locale-specific
%y	Year without century 00-99	84, 05
%Y	Year with century on input: 00 to 68 prefixed by 20 69 to 99 prefixed by 19	1984, 2005
%C	Century	19, 20
%D	Date formatted %m/%d/%y	05/27/84, 07/07/05
%u	Weekday 1-7 Monday is 1	7, 4
%n	Newline on output or Arbitrary whitespace on input
%t	Tab on output or Arbitrary whitespace on input