[R] Comparing two date columns

[David Winsemius]

On Feb 21, 2010, at 2:19 PM, Newbie19_02 wrote:

>
> Hi everyone,
>
> I have another fairly simple question.  I want to take the earliest  
> of two
> dates from these two date columns.  I've tried converting the dates to
> numbers and just get a vector full of NA's.  I've also tried using  
> the chron
> function to compare the two and have been unsuccessful.  I then  
> tried to
> use:temp.2 <- as.POSIXct(strptime(temp, '%d/%m/%Y')) where temp is  
> character
> vector of one of the date columns this did not work either.  I'm not  
> sure
> what to do now.
>
> date_1             date_2
> 2005-11-25       <NA>
> 2007-10-23       <NA>
> <NA>               1999-12-13
> 2006-01-25       <NA>
> 2006-06-12       <NA>
> 2005-08-08       <NA>
> 2007-12-12       <NA>
> 2008-04-29       <NA>
> 2005-03-28       <NA>
> 2004-11-18 2000-11-02
> 2006-03-16       <NA>
> 2007-01-17       <NA>

We cannot tell from that output what data type you are working with.  
You may not be working with Dates at all. You also have not offered  
the code that is not working. If they are dates, then pmin should work  
well.

 > pmin(as.Date("2004-11-18"), as.Date("2000-11-02"))
[1] "2000-11-02"

Next time use dput to allow unambiguous communication. (The fact that  
you are not using either dput or dump suggests you have not yet spent  
enough effort at reading the Posting Guide.)

-- 
David
>
>
> Thanks for your help,
> Natalie
> -- 
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>
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