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transforming dates

9 messages · reichm@@j m@iii@g oii sbcgiob@i@@et, Bert Gunter, Rui Barradas +3 more

Original
reichm@@j m@iii@g oii sbcgiob@i@@et
# 
R-Help Forum

 

I have a data set that contains a date field but the dates are in two
formats

 

11/7/2016            dd/mm/yyyy

14-07-16               dd-mm-yy

 

How would I go about correcting this problem. Should I separate the dates,
format them , and then recombine?

 

Sincerely

 

Jeff Reichman

(314) 457-1966
Bert Gunter
# 
Well, one way to do it is via regex's -- no splitting and recombining
needed.
Note: This will convert a factor into a character vector.
/ and \
[1] "11/7/2016"  "14/07/2016"

I leave it to you as an exercise to either convert 7 to 07 or vice-versa if
you want to do this.
Note, if you have spaces sprinkled inconsistently around your separators,
you'll have to work a bit harder with your regex.

Cheers,
Bert



Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Sat, Nov 2, 2019 at 7:25 PM <reichmanj at sbcglobal.net> wrote:

            

      
      
      
    

        

      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Rui Barradas
    

    

      
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Hello,

I believe the simplest is to use package lubridate. Its functions try 
several formats until either one is right or none fits the data.

x <- c('11/7/2016', '14-07-16')
lubridate::dmy(x)
#[1] "2016-07-11" "2016-07-14"


The order dmy must be the same for all vector elements, if not

y <- c('11/7/2016', '14-07-16', '2016/7/11')
lubridate::dmy(y)
#[1] "2016-07-11" "2016-07-14" NA
#Warning message:
# 1 failed to parse.


Hope this helps,

Rui Barradas

?s 02:25 de 03/11/19, reichmanj at sbcglobal.net escreveu:

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Bert Gunter
    

    

      
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Rui is right -- lubridate functionality and robustness is better -- but
just for fun, here is a simple function, poorly named reformat(), that
splits up the date formats, cleans them up and standardizes them a bit, and
spits them back out with a sep character of your choice (your original
split and recombine suggestion). Lubridate probably does something similar
but more sophisticated, but maybe it's worthwhile to see how one can do it
using basic functionality. This only requires a few short lines of code.

reformat <- function(z, sep = "-"){
   z <- gsub(" ","",z) ## remove blanks
   ## break up dates into 3 component pieces and convert to matrix
   z <- matrix(unlist(strsplit(z, "-|/")), nrow = 3)
   ## add "0" in front of single digit in dd and mm
   ## add "20" in front  of "yy"
   for(i in 1:2) z[i, ] <- gsub("\\<([[:digit:]])\\>","0\\1",z[i, ])
   z[3, ] <- sub("\\<([[:digit:]]{2})\\>","20\\1",z[3, ])
   ## combine back into single string separated by sep
   paste(z[1, ],z[2, ],z[3, ], sep = sep)
}

## Testit

            

      
      
      
    

        
[1] "01-22-2015" "01-05-2015" "11-07-2016" "14-07-2016"

            

      
      
      
    

        
[1] "01/22/2015" "01/05/2015" "11/07/2016" "14/07/2016"

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

        
On Sun, Nov 3, 2019 at 12:15 AM Rui Barradas <ruipbarradas at sapo.pt> wrote:

        

            

      
      
      
    

        

      
      
    

        

      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      David Winsemius
    

    

      
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On 11/3/19 11:51 AM, Bert Gunter wrote:

            

      
      
      
    

        
If one wants to investigate existing efforts at automatic date _and_ 
time reformatting, then do not forget Dirk's anytime package:


https://cran.r-project.org/web/packages/anytime/index.html

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Bert Gunter
    

    

      
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Yes, indeed.

Thanks, David.

Cheers,
Bert

On Sun, Nov 3, 2019 at 12:22 PM David Winsemius <dwinsemius at comcast.net>
wrote:

            

      
      
      
    

        

      
      
    

        

      
      
    

            

      
      
      
    

        

      
      
    

        

      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Peter Dalgaard
    

    

      
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=======

Hey, that's my birthday! Err, no it isn't... ;-)

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Spencer Graves
    

    

      
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On 2019-11-03 17:04, Peter Dalgaard wrote:

            

      
      
      
    

        
????? Is that November 11 of 2019 or March 19 of 2011 or 11 March 2019?


 ????? The English still use stones as a unit of mass, and most of the 
US still steadfastly refuses to seriously consider metrication or? ISO 
8601.? I know an architect in the US, who has worked on several 
different projects every year for the past 40 years only one of which 
has been in metric units.


 ?????? Binary, octal or hex is superior to decimal, except for the fact 
that most humans have 10 digits on hands and feet.? And decimal is 
vastly superior to arithmetic in mixed bases, e.g., adding miles, rods, 
yards, feet, inches, and 64ths.


 ????? Spencer Graves

  
  


  


      

    

    

      
      

        


  

        

      Spencer Graves
    

    

      
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On 2019-11-03 17:04, Peter Dalgaard wrote:

            

      
      
      
    

        
????? Is that November 3 of 2019 or March 19 of 2011 or 11 March 2019?? 
[please excuse the typo in the earlier response]


 ????? The English still use stones as a unit of mass, and most of the 
US still steadfastly refuses to seriously consider metrication or? ISO 
8601.? I know an architect in the US, who has worked on several 
different projects every year for the past 40 years only one of which 
has been in metric units.


 ?????? Binary, octal or hex is superior to decimal, except for the fact 
that most humans have 10 digits on hands and feet.? And decimal is 
vastly superior to arithmetic in mixed bases, e.g., adding miles, rods, 
yards, feet, inches, and 64ths.


 ????? Spencer Graves