R_Date_time_Handle_R Notebook

R_Date_time_Handle_R Notebook

1、取出当前日期

Sys.Date()

[1] "2017-07-08"

2、在R中日期实际是double类型，是从1970年1月1日以来的天数

typeof(Sys.Date())
# [1] "double"

3、转换为日期

用as.Date()可以将一个字符串转换为日期值，默认格式是yyyy-mm-dd。

as.Date("2007-02-01")   #得到"2007-02-01"，显示为字符串，但实际是用double存储的
as.double(as.Date("1970-01-01"))  #结果为0，是从1970年1月1日以来的天数。

# 可以把定制的日期字符串转换为日期型
as.Date("2007年2月1日", "%Y年%m月%d日") 
# [1] "2007-02-01"

x<-as.Date("1970-01-01")   
unclass(x)   
# [1] 0  

unclass(as.Date("1970-02-01")) #19700201代表第31天  
# [1] 31  
# unclass可以将日期变成以天来计数，
# 比如1970-02-01输出的31，就代表着距离1970-01-01有31天。

格式 意义 %Y 年份，以四位数字表示，2007 %m 月份，以数字形式表示，从01到12 %d 月份中当的天数，从01到31 %b 月份，缩写，Feb %B 月份，完整的月份名，指英文，February %y 年份，以二位数字表示，07

4、把日期值输出为字符串

today <- Sys.Date()
format(today, "%Y年%m月%d日")
# [1] "2014年10月29日"

5、计算日期差

由于日期内部是用double存储的天数，所以是可以相减的。

today <- Sys.Date()
gtd <- as.Date("2011-07-01")   
today - gtd
# Time difference of 1216 days  

用difftime()函数可以计算相关的秒数、分钟数、小时数、天数、周数

difftime(today, gtd, units="weeks")  
#还可以是“secs”, “mins”, “hours”, “days”
# Time difference of 173.7143 weeks

6. 日期型数据

在R中自带的日期形式为：as.Date();以数值形式存储；

对于规则的格式，则不需要用format指定格式； 如果输入的格式不规则，可以通过format指定的格式读入；

标准格式： 年-月-日或者年/月/日； 如果不是以上二种格式，则会提供错误；

as.Date('23-2013-1')
# 错误于charTo按照Date(x) : 字符串的格式不够标准明确

as.Date('23-2013-1',format='%d-%Y-%m')
# [1] "2013-01-23"

格式 意义 %Y 年份，以四位数字表示，2007 %m 月份，以数字形式表示，从01到12 %d 月份中当的天数，从01到31 %b 月份，缩写，Feb %B 月份，完整的月份名，指英文，February %y 年份，以二位数字表示，07

其它日期相关函数

weekdays() 取日期对象所处的周几； months() 取日期对象的月份； quarters() 取日期对象的季度；

7. POSIX类

The POSIXct class stores date/time values as the number of seconds since January 1, 1970, while the POSIXlt class stores them as a list with elements for second, minute, hour, day, month, and year, among others.

POSIXct 是以1970年1月1号开始的以秒进行存储，如果是负数，则是1970年以前；正数则是1970年以后。

POSIXlt 是以列表的形式存储：年、月、日、时、分、秒；作用是打散时间，把时间分成年、月、日、时、分、秒，并进行存储。

today <- Sys.time()  
unclass(as.POSIXlt(today))  
# $sec
# [1] 49.00171
# 
# $min
# [1] 15
# 
# $hour
# [1] 0
# 
# $mday
# [1] 4
# 
# $mon
# [1] 6
# 
# $year
# [1] 117
# 
# $wday
# [1] 2
# 
# $yday
# [1] 184
# 
# $isdst
# [1] 0
# 
# $zone
# [1] "CST"
# 
# $gmtoff
# [1] 28800
# 
# attr(,"tzone")
# [1] ""    "CST" "CDT"

mydate = as.POSIXlt('2005-4-19 7:01:00')
names(mydate)

默认情况下，日期之前是以/或者-进行分隔，而时间则以：进行分隔；

输入的标准格式为：日期 时间（日期与时间中间有空隔隔开）

时间的标准格式为：时:分 或者 时:分:秒；

如果输入的格式不是标准格式，则同样需要使用strptime函数，利用format来进行指定；

## 生成案例数据
Dates <- c("2009-09-28","2010-01-15")
Times <- c( "23:12:55", "10:34:02")
charvec <- timeDate(paste(Dates, Times))
timeDate(charvec)

#取系统的时间
Sys.timeDate()

#一个月的第一天
timeFirstDayInMonth()

#一个月的最后一天
timeLastDayInMonth()

#一周当中第几天
dayOfWeek()

#一年当中的第几天
dayOfYear()

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"

now_ct <- Sys.time()  
now_ct  
# [1] "2015-10-29 21:36:41 CST"  
class(now_ct)  
# [1] "POSIXct" "POSIXt"   

date <- as.Date(now_ct)  
date  
# [1] "2015-10-29" 

# 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)

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

POSIXct 格式

主要特点：以秒进行存储。

today<-Sys.time()  
today  
# [1] "2016-06-06 20:42:22 CST"  

unclass(as.POSIXct(today))  
# [1] 1465216942  
# 解读：比如今天，unclass之后，
# 代表今天2016-06-06距离1970-01-01为1465216942秒。
#GMT代表时区，德意志时间，CST也代表时区

8.如何在循环、函数中，输出实时时间消耗

t1 = Sys.time()  
for (i in 1:5){  
a=a+1  
b=a*a  
print(difftime(Sys.time(), t1, units = 'sec'))  
}  

9. How to change the locale of R in RStudio?

The R console is in my native language, how can I set R to English?

1. Go into R installation directory, i.e. C:Files
   

2. From there go into the subfolder etc/

3. Open with a text editor (i.e. Notepad) the file Rconsole

4. Look into the file for the line language =

5. Replace such line with language = en

6. Save and close the Rconsole file, then run Rgui again, and the interface will be in English

R version 3.1.3

input string 1 is invalid in this locale

The issue is that you have a French/Chinese etc locale, which uses different month and day names and abbreviations. You can change to the English locale by running:

Sys.setlocale('LC_ALL','English');

[1] "LC_COLLATE=English_United States.1252;LC_CTYPE=English_United States.1252;LC_MONETARY=English_United States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252"

10. How to update R in RStudio using installr package for Windows

## How to update R in RStudio using installr package (for Windows)
## paste this into the console and run the commands
## "The updateR() command performs the following: finding the latest R version, downloading it, running the installer, deleting the installation file, copy and updating old packages to the new R installation."
## more info here: https://cran.r-project.org/web/packages/installr/index.html

# The installr package seems like a great solution but unfortunately is only for Windows.

# installing/loading the package，load /install+load installr  
if(!require(installr)){ 
  install.packages("installr"); 
  require(installr)} 

# using the installr package, install, move, update.package, quit R.
## Watch for small pop up windows. There will be many questions and they don't always pop to the front. 
## Note: It warns that it might work better in Rgui but I did it in Rstudio and it worked just fine. 
# this will start the updating process of your R installation.  
# It will check for newer versions, and if one is available, will guide you through the decisions you'd need to make.
updateR()

11. R sessionInfo, version, packageStatus

# session, version, packageStatus
sessionInfo()
version

# get r version
R.version.string

packageStatus()