[R] identify time span in date vector

[Fischer, Felix]

Dear Petr,

thanks for taking your time. 

For this input, the first element should be selected since there are more than 3 more dates within one year (basically, all other dates are within one year) and at least one of them is more than 3 month later.

In the meantime, I came up with some code (probably) doing what I want:

identify_first_date = function(dates)
{
within_one_year = as.matrix(dist(dates)) < 366   					### next dates in same year?
within_one_year[upper.tri(within_one_year, diag=TRUE)]=FALSE

within_one_month = as.matrix(dist(dates)) < 91 					### next dates within 90 days?
within_one_month[upper.tri(within_one_month, diag=TRUE)]=FALSE

dates[
	which(
	apply(within_one_year,2,sum) > apply(within_one_month,2,sum) & 		### more dates in one year than in one month
	apply(within_one_year,2,sum) >=3 						### more than 4 dates in one year
	)[1]]
}

I guess, the code could be improved, though, it takes some time.

Best,
Felix


-----Ursprüngliche Nachricht-----
Von: Petr PIKAL [mailto:petr.pikal at precheza.cz] 
Gesendet: Mittwoch, 4. April 2012 09:47
An: Fischer, Felix
Cc: r-help at r-project.org
Betreff: Odp: [R] identify time span in date vector

Hi

Can you please be more specific? Based on this input, what do you want as a result?

> set.seed(111)
> dates = as.Date(sort(rnorm(10,3000,100)), origin = "2000-1-1") dates
 [1] "2007-08-01" "2007-10-21" "2007-12-08" "2007-12-15" "2008-01-29" 
"2008-02-14" "2008-02-16" "2008-03-01"
 [9] "2008-04-02" "2008-04-11"
>

Regards
Petr

> 
> Hello everyone,
> 
> i try to identify the first element of a date vector, for which the 
> following condition holds: at least 3 more dates within the next 365
days,
> but at least one of these must be between 3-12 month later.
> 
> dates = as.Date(sort(rnorm(10,3000,100)), origin = "2000-1-1")
> 
> Has anyone an idea how to do this economically? I'll need to apply 
> this
to
> a large dataset with date vectors of various lengths and I can think
only 
> of quite difficult algorithms :(
> 
> Any ideas would be appreciated,
> Felix
> 
> 
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