R help - Mar 2010 - Numeric to Date

Is there easy way to convert numeric to date?

For example:

If I have, 

	a = as.Date("2010-03-04")

And, if run
> as.numeric(a)
 [1] 14672

Is there any function that I can use to convert 14672 back to the date.

Thx in advance, 
Brijesh

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On Wed, 10 Mar 2010, GULATI, BRIJESH (Global Markets FF&O NY) wrote:
> Is there easy way to convert numeric to date?
>
> For example:
>
> If I have,
>
> 	a = as.Date("2010-03-04")
>
> And, if run
>
>> as.numeric(a)
> [1] 14672
>
> Is there any function that I can use to convert 14672 back to the date.
You can use as.Date(). In base R, you additionally need to specify
   origin = "1970-01-01"
because that is what is used in R. If you load the package "zoo" then
the
default is set automatically:

R> a <- as.Date("2010-03-04")
R> a
[1] "2010-03-04"
R> b <- as.numeric(a)
R> b
[1] 14672
R> as.Date(b)
Error in as.Date.numeric(b) : 'origin' must be supplied
R> as.Date(b, origin = "1970-01-01")
[1] "2010-03-04"
R> library("zoo")
R> as.Date(b)
[1] "2010-03-04"

hth,
Z
> Thx in advance,
> Brijesh
>
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>
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http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

On Mar 10, 2010, at 3:29 PM, GULATI, BRIJESH (Global Markets FF&O NY) wrote:
> Is there easy way to convert numeric to date?
> 
> For example:
> 
> If I have, 
> 
> 	a = as.Date("2010-03-04")
> 
> And, if run
> 
>> as.numeric(a)
> [1] 14672
> 
> Is there any function that I can use to convert 14672 back to the date.
> 
> Thx in advance, 
> Brijesh
> as.Date(14672, origin = "1970-01-01")
[1] "2010-03-04"


Of course, you would have to know that R stores dates internally as the number
of days since 1970-01-01, which is curiously not defined in the help page for
?as.Date, but is on ?Date, which is in the See Also of the former.

HTH,

Marc Schwartz

numToPOSIXct <- function(v) { 
  now <- Sys.time() 
  Epoch <- now - as.numeric(now) 
  Epoch + v 
} 

Try this - where v is your numeric version of date
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