在R中更改日期格式 [英] Changing date format in R

问题描述

我在R中有一些非常简单的数据，需要更改日期格式：

 日期中点
 1 31/08/2011 0.8378 
 2 31/07/2011 0.8457 
 3 30/06/2011 0.8147 
 4 31/05/2011 0.7970 
 5 30/04/2011 0.7877 
 31 31/03/2011 0.7411 
 7 28/02/2011 0.7624 
 8 31/01/2011 0.7665 
 9 31/12/2010 0.7500 
 10 30/11/2010 0.7734 
 31 31/10/2010 0.7511 
 12 30/09/2010 0.7263 
 13 31/08/2010 0.7158 
 14 31/07/2010 0.7110 
 15 30/06/2010 0.6921 
 16 31/05/2010 0.7005 
 17 30/04/2010 0.7113 
 18 31/03/2010 0.7027 
 19 28 / 02/2010 0.6973 
 20 31/01/2010 0.7260 
 21 31/12/2009 0.7154 
 22 30/11/2009 0.7287 
 23 31/10/2009 0.7375 
  

而不是％d /％m /％Y ，我想用标准R格式％Y-％m-％d

我做这个改变？我已经尝试过：

$ p $ nzd $ date< - format（as.Date（nzd $ date），％Y /％但是，这只是切断了一年，并增加了一天的零：
$> b
$ b

/ p>



  [1]0031/08/200031/07/200030/06/200031 / 05/200030/04/20
 [6]0031/03/200028/02/200031/01/200031/12/200030/11 / 20
 [11]0031/10/200030/09/200031/08/200031/07/200030/06/20
 [ 16]0031/05/200030/04/200031/03/200028/02/200031/01/20
 [21]0031/12/20 0030/11/200031/10/200030/09/200031/08/20
 [26]0031/07/200030/06/20 0031/05/200030/04/200031/03/20
 [31]0028/02/200031/01/200031/12/20 0030/11/200031/10/20
 [36]0030/09/200031/08/200031/07/200030/06/200031 / 05/20
  

感谢！


解决方案

这里有两个步骤：





• 解析数据。你的例子不是完全可重复的，是文件中的数据，还是文本或因子变量中的变量？让我们假设后者，那么如果你的data.frame被称为X，你可以做


lockquote
$ $ p $ （$ X $ date），％d /％m /％Y）
newdate 列应该是类型的

  
  

  日期。

  
  
  
  
  
  • 格式化数据。这是调用 format（）或 strftime（）：
  
  
  
  
  

  
  

   格式（X $ newdate，％Y-％m-％d）
    

  
  

  更完整的例子：
  
  

    R> nzd < -  data.frame（date = c（31/08/2011，31/07/2011，30/06/2011），
   + mid = c（0.8378,0.8457， 0.8147））
   R> nzd 
  日期中
   1 31/08/2011 0.8378 
   2 31/07/2011 0.8457 
   3 30/06/2011 0.8147 
   R> nzd $ newdate<  -  strptime（as.character（nzd $ date），％d /％m /％Y）
   R> nzd $ txtdate<  -  format（nzd $ newdate，％Y-％m-％d）
   R> nzd 
  日期中值新值txtdate 
   1 31/08/2011 0.8378 2011-08-31 2011-08-31 
   2 31/07/2011 0.8457 2011-07-31 2011-07- 31 
   3 30/06/2011 0.8147 2011-06-30 2011-06-30 
   R> 
    

  第三列和第四列的区别在于： newdate 是类日期，而 txtdate 是字符。

  
  

  I have some very simple data in R that needs to have its date format changed:

   date midpoint
  1   31/08/2011   0.8378
  2   31/07/2011   0.8457
  3   30/06/2011   0.8147
  4   31/05/2011   0.7970
  5   30/04/2011   0.7877
  6   31/03/2011   0.7411
  7   28/02/2011   0.7624
  8   31/01/2011   0.7665
  9   31/12/2010   0.7500
  10  30/11/2010   0.7734
  11  31/10/2010   0.7511
  12  30/09/2010   0.7263
  13  31/08/2010   0.7158
  14  31/07/2010   0.7110
  15  30/06/2010   0.6921
  16  31/05/2010   0.7005
  17  30/04/2010   0.7113
  18  31/03/2010   0.7027
  19  28/02/2010   0.6973
  20  31/01/2010   0.7260
  21  31/12/2009   0.7154
  22  30/11/2009   0.7287
  23  31/10/2009   0.7375
  

  Rather than %d/%m/%Y, I would like it in the standard R format of %Y-%m-%d

  How can I make this change? I have tried:

  nzd$date <- format(as.Date(nzd$date), "%Y/%m/%d")
  

  But that just cut off the year and added zeros to the day:

   [1] "0031/08/20" "0031/07/20" "0030/06/20" "0031/05/20" "0030/04/20"
   [6] "0031/03/20" "0028/02/20" "0031/01/20" "0031/12/20" "0030/11/20"
   [11] "0031/10/20" "0030/09/20" "0031/08/20" "0031/07/20" "0030/06/20"
   [16] "0031/05/20" "0030/04/20" "0031/03/20" "0028/02/20" "0031/01/20"
   [21] "0031/12/20" "0030/11/20" "0031/10/20" "0030/09/20" "0031/08/20"
   [26] "0031/07/20" "0030/06/20" "0031/05/20" "0030/04/20" "0031/03/20"
   [31] "0028/02/20" "0031/01/20" "0031/12/20" "0030/11/20" "0031/10/20"
   [36] "0030/09/20" "0031/08/20" "0031/07/20" "0030/06/20" "0031/05/20"
  

  Thanks!

  解决方案

  There are two steps here:

  • Parse the data. Your example is not fully reproducible, is the data in a file, or the variable in a text or factor variable? Let us assume the latter, then if you data.frame is called X, you can do

   X$newdate <- strptime(as.character(X$date), "%d/%m/%Y")
  

  Now the newdate column should be of type Date.

  • Format the data. That is a matter of calling format() or strftime():

   format(X$newdate, "%Y-%m-%d")
  

  A more complete example:

  R> nzd <- data.frame(date=c("31/08/2011", "31/07/2011", "30/06/2011"), 
  +                    mid=c(0.8378,0.8457,0.8147))
  R> nzd
          date    mid
  1 31/08/2011 0.8378
  2 31/07/2011 0.8457
  3 30/06/2011 0.8147
  R> nzd$newdate <- strptime(as.character(nzd$date), "%d/%m/%Y")
  R> nzd$txtdate <- format(nzd$newdate, "%Y-%m-%d")
  R> nzd
          date    mid    newdate    txtdate
  1 31/08/2011 0.8378 2011-08-31 2011-08-31
  2 31/07/2011 0.8457 2011-07-31 2011-07-31
  3 30/06/2011 0.8147 2011-06-30 2011-06-30
  R> 
  

  The difference between columns three and four is the type: newdate is of class Date whereas txtdate is character.

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