[R] Mixed Date Formats

[Sarah Goslee]

I'm assuming you actually want the date column to be character, not factor:
SampleData <- structure(list(id = 1:7, value = c(5813L, 8706L, 4049L, 5877L,
1375L, 2223L, 3423L), date = c("19-Dec-11", "07-Dec-11", "06/05/11",
"05/12/11", "31/12/2011", "10/19/2011", "01/22/2011")), .Names = c("id",
"value", "date"), row.names = c(NA, -7L), class = "data.frame")

  id value       date
1  1  5813  19-Dec-11
2  2  8706  07-Dec-11
3  3  4049   06/05/11
4  4  5877   05/12/11
5  5  1375 31/12/2011
6  6  2223 10/19/2011
7  7  3423 01/22/2011

Given this assemblage of dates, there is a lot of ambiguity. The first
two are clear, but is the third in May or June? Is the fourth May or
December?

I had hoped that the number of digits in the year provided a clue, but
#5 is clearly dd/mm/yyyy while #7 is mm/dd/yyyy

Or actually, #3 could be yy/mm/dd too.

I don't see a way to programmatically solve your problem, because
there is no clear way to parse all of these dates because of the
ambiguity.

You could get some of them by checking for values outside the bounds
of legitimate month numbers, or just try it and discard the values
that give NA results:
> as.Date("01/22/2011", "%m/%d/%Y")
[1] "2011-01-22"
> as.Date("01/22/2011", "%d/%m/%Y")
[1] NA

But you need more information to figure out the rest.

Sarah

On Wed, Jul 29, 2015 at 5:15 PM, farnoosh sheikhi <farnoosh_81 at yahoo.com> wrote:
> Hi Sarah,
>
> Thanks for getting back to me.
> Here is an example of my data:
> SampleData <- structure(list(id = 1:7, value = c(5813L, 8706L, 4049L, 5877L,
>                                              1375L, 2223L, 3423L), date =
> structure(c(4L, 3L, 2L, 1L, 7L,
>
> 6L, 5L), .Label = c("05/12/11", "06/05/11", "07-Dec-11",
>
> "19-Dec-11", "01/22/2011", "10/19/2011", "31/12/2011"
>
> ), class = "factor")), .Names = c("id", "value", "date"), row.names = c(NA,
>
> -7L), class = "data.frame")
> SampleData
>
> Thanks for your help:).
>
>
>
>
>
>
> On Wednesday, July 29, 2015 1:50 PM, Sarah Goslee <sarah.goslee at gmail.com>
> wrote:
>
>
> On Wed, Jul 29, 2015 at 2:45 PM, farnoosh sheikhi via R-help
>
> <r-help at r-project.org> wrote:
>>  Hi Arun,
>> Hope all is well with you. I have a data with a column for date.The date
>> format is mixed. There are date values with Month/Day/Year format and values
>> with Day/Month/Year format.I don't know how to unify it.I really appreciate
>> your help.Thanks.
>
>
> You sent this to the R-help list, not just to Arun, so I'm assuming
> this is an R question. The best way to get help is to provide a sample
> of your data using dput() and to clearly specify what you would like
> as the result - "unify" is a bit vague. paste(x, collapse="") could be
> considered unification, after all.
>
> Sarah