日期时间函数
Sys.Date( ) #returns today's date. date() #returns the current date and time. # print today's date today <-Sys.Date() format(today, format="%B %d %Y") "June 20 2007" # convert date info in format 'mm/dd/yyyy' strDates <- c("01/05/1965", "08/16/1975") dates <- as.Date(strDates, "%m/%d/%Y") # convert dates to character data strDates <- as.character(dates)
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as.Date('1915-6-16') [1] "1915-06-16" as.Date('1990/02/17') [1] "1990-02-17" as.Date('1/15/2001',format='%m/%d/%Y') [1] "2001-01-15" as.Date('April 26, 2001',format='%B %d, %Y') [1] "2001-04-26" as.Date('22JUN01',format='%d%b%y') # %y is system-specific; use with caution [1] "2001-06-22" bdays = c(tukey=as.Date('1915-06-16'),fisher=as.Date('1890-02-17'), + cramer=as.Date('1893-09-25'), kendall=as.Date('1907-09-06')) weekdays(bdays) tukey fisher cramer kendall "Wednesday" "Monday" "Monday" "Friday" dtimes = c("2002-06-09 12:45:40","2003-01-29 09:30:40", + "2002-09-04 16:45:40","2002-11-13 20:00:40", + "2002-07-07 17:30:40") dtparts = t(as.data.frame(strsplit(dtimes,' '))) row.names(dtparts) = NULL thetimes = chron(dates=dtparts[,1],times=dtparts[,2], + format=c('y-m-d','h:m:s')) thetimes [1] (02-06-09 12:45:40) (03-01-29 09:30:40) (02-09-04 16:45:40) [4] (02-11-13 20:00:40) (02-07-07 17:30:40) dts = c("2005-10-21 18:47:22","2005-12-24 16:39:58", + "2005-10-28 07:30:05 PDT") as.POSIXlt(dts) [1] "2005-10-21 18:47:22" "2005-12-24 16:39:58" [3] "2005-10-28 07:30:05" dts = c(1127056501,1104295502,1129233601,1113547501, + 1119826801,1132519502,1125298801,1113289201) mydates = dts class(mydates) = c('POSIXt','POSIXct') mydates [1] "2005-09-18 08:15:01 PDT" "2004-12-28 20:45:02 PST" [3] "2005-10-13 13:00:01 PDT" "2005-04-14 23:45:01 PDT" [5] "2005-06-26 16:00:01 PDT" "2005-11-20 12:45:02 PST" [7] "2005-08-29 00:00:01 PDT" "2005-04-12 00:00:01 PDT" mydate = strptime('16/Oct/2005:07:51:00',format='%d/%b/%Y:%H:%M:%S') [1] "2005-10-16 07:51:00" ISOdate(2005,10,21,18,47,22,tz="PDT") [1] "2005-10-21 18:47:22 PDT" thedate = ISOdate(2005,10,21,18,47,22,tz="PDT") format(thedate,'%A, %B %d, %Y %H:%M:%S') [1] "Friday, October 21, 2005 18:47:22" mydate = as.POSIXlt('2005-4-19 7:01:00') names(mydate) [1] "sec" "min" "hour" "mday" "mon" "year" [7] "wday" "yday" "isdst" mydate$mday [1] 19
posted on 2016-03-23 14:25 MartinChau 阅读(280) 评论(0) 编辑 收藏 举报