[R] Question about time series

[Christian Schulz]

Hi

 >>TODAY           <- as.POSIXlt('2004-01-17')
 >>LYTODAY  <- as.POSIXlt('2003-01-17')
 >>DAYS <- TODAY-LYTODAY
 >>DAYS
Time difference of 365 days
 >>DAYS[[1]]
[1] 365

perhaps it helps,
Christian


Dennis Fisher wrote:

> I have data in the following format:
>
> > DATE
> [1] "01/13/2004"
>
> In order to find the difference between two data points, I presently 
> use brute force to calculate the day of the year:
>
> > strptime(DATE, format="%m/%d/%Y")$yday
> [1] 12
>
> Although this works, it may not be robust over different years.  I 
> assume that R is sufficiently clever that a much simpler approach 
> exists, e.g., can I calculate the number of days since some fixed 
> time?  Unfortunately, the man pages and FAQ did not lead me to an 
> obvious solution.
>
> Any help appreciated.
>
> Dennis
>
> Dennis Fisher MD
> P < (The "P Less Than" Company)
> Phone: 1-866-PLessThan (1-866-753-7784)
> Fax: 1-415-564-2220
> www.PLessThan.com
>
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