[R] strange Sys.Date() side effect

[Czerminski, Ryszard]

Basically I want to create a string vector where first element is a
date.

>> Note that if you supply c() with objects of different types (as you
have),
>> the results will probably not be what you wanted.

This is the key. I assumed (not correctly)
that Sys.Date() generates a character

> Sys.Date()
[1] "2012-01-13"

but as you point out:

> class(Sys.Date())
[1] "Date"
  
and it is the best to provide c() with arguments of the same type
so, in the end, explicitely casting Sys.Date() to character works for
me:

> N <- 2; c(as.character(Sys.Date()), sprintf('N=%d', N))
[1] "2012-01-13" "N=2"

Thanks!

Ryszard


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-----Original Message-----
From: MacQueen, Don [mailto:macqueen1 at llnl.gov] 
Sent: Thursday, January 12, 2012 5:27 PM
To: Czerminski, Ryszard; r-help at r-project.org
Subject: Re: [R] strange Sys.Date() side effect

My best guess is that you are misunderstanding what the c() function
does.
I'd suggest reading the help page for c, obtained by typing
  ?c
Note that if you supply c() with objects of different types (as you
have),
the results will probably not be what you wanted.

Given what c() does, your output and warning message make sense. But I'm
unable to figure out what you're really trying to do. Something like
this,
perhaps?

> N <- 2; sprintf('N = %d', N)
[1] "N = 2"


-Don


-- 
Don MacQueen

Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062





On 1/10/12 5:04 AM, "Czerminski, Ryszard"
<Ryszard.Czerminski at astrazeneca.com> wrote:

>Any ideas what is the problem with this code?
>
>> N <- 2; c(Sys.Date(), sprintf('N = %d', N))
>[1] "2012-01-10" NA
>Warning message:
>In as.POSIXlt.Date(x) : NAs introduced by coercion
>
>Best regards,
>Ryszard
>
>Ryszard Czerminski
>AstraZeneca Pharmaceuticals LP
>35 Gatehouse Drive
>Waltham, MA 02451
>USA
>781-839-4304
>ryszard.czerminski at astrazeneca.com
>
>
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