[R] re placing the dates format in R for exporting the data set...

[David Winsemius]

On Nov 18, 2009, at 11:00 PM, ychu066 wrote:

>
> hey Jim ,
>
> I have solve the column name problems now.  But i am still unable to  
> read
> the date in R ...
>
> toms_dat<- replace(toms_dat, toms_dat ==2009-08-24, 6)

replace needs its first argument to be a vector, while you have given  
it a dataframe.

Look at these examples:
 > toms <- data.frame(a=letters[1:10], b=Sys.Date() + 1:10)
 > toms
    a          b
1  a 2009-11-20
2  b 2009-11-21
3  c 2009-11-22
4  d 2009-11-23
5  e 2009-11-24
6  f 2009-11-25
7  g 2009-11-26
8  h 2009-11-27
9  i 2009-11-28
10 j 2009-11-29
 > replace(toms$b, toms$b=="2009-11-23", 6)
Error in as.Date.numeric(value) : 'origin' must be supplied

Notice that this did not
 > replace(toms$b, toms$b=="2009-11-23", "2008-01-01")
  [1] "2009-11-20" "2009-11-21" "2009-11-22" "2008-01-01" "2009-11-24"  
"2009-11-25" "2009-11-26"
  [8] "2009-11-27" "2009-11-28" "2009-11-29"
 > toms
    a          b
1  a 2009-11-20
2  b 2009-11-21
3  c 2009-11-22
4  d 2009-11-23
5  e 2009-11-24
6  f 2009-11-25
7  g 2009-11-26
8  h 2009-11-27
9  i 2009-11-28
10 j 2009-11-29

Notice that the replace() operation did not do anything to "toms". If  
you had wanted it to, you would have needed to do:

toms$b <- replace(toms$b, toms$b=="2009-11-23", "2008-01-01")

Now, if you want further assistance you need to provide a working  
excaple that has the same features as your problem. Use str(toms_dat)  
to see what type your columns are ant then perhaps:

dput(head(toms_dat))

or:

dump("toms_dat", file=stdout() )

or if toms_dat is big, then:

smalltoms <- head(toms_dat)
dump("smalltoms", stdout() )


>
> the toms_dat is a data frame , and I  want to replace the date to be a
> single number eg:1,2,3, ....
>
> regards,
> Tom.
>
>
>
>
>
> jholtman wrote:
>>
>> First of all '2009-08-06' is 1995; this is probably not what you were
>> expecting.  What do you what your expression to do?  Is 'toms_dat' a
>> dataframe?  if so, your expression 'toms_dat ==2009-08-06' seem
>> strange.  So tell us what you want to do, not how you want to do it.
>>
>> On Tue, Nov 17, 2009 at 4:54 PM, ychu066 <ychu066 at aucklanduni.ac.nz>
>> wrote:
>>>
>>> hi everyone, i am having difficulties with replacing the dates  
>>> format in
>>> R
>>> for exporting the data set...
>>>
>>> eg: the code that i used was
>>> toms_dat<- replace(toms_dat, toms_dat ==2009-08-06, 2)
>>> toms_dat<- replace(toms_dat, toms_dat ==2009-08-04, 1)
>>>
>>> but when i export the data as into txt file or excel file the  
>>> dates come
>>> up
>>> with very large numbers .....:drunk:
>>>
>>> please help me ...=)
>>> --
>>> View this message in context:
>>> http://old.nabble.com/replacing-the-dates-format-in-R-for-exporting-the-data-set...-tp26396492p26396492.html
>>> Sent from the R help mailing list archive at Nabble.com.
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>
>>
>>
>> -- 
>> Jim Holtman
>> Cincinnati, OH
>> +1 513 646 9390
>>
>> What is the problem that you are trying to solve?
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>
> -- 
> View this message in context: http://old.nabble.com/replacing-the-dates-format-in-R-for-exporting-the-data-set...-tp26396492p26420068.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT