Dear David,
thanks for your suggestion.
However, when applied to
dates = as.Date(c("2001-1-1", "2001-1-3", "2001-1-12", "2001-1-13",
"2001-4-20"))
it doesn't behave like i want...
> which( dates[4:(length(dates))] -dates[1:(length(dates)-3)] <365 &
dates[3:(length(dates)-1)] -dates[1:(length(dates)-3)] > 90)
integer(0)
The condition is true for the first element of the vector, there are 4 more
dates within one year and one ("2001-4-20") is more than 90 days away.
I came up with the following solution:
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]]
}
identify_first_date(dates)
[1] "2001-01-01"
However, this takes some time (couple of minutes) with my dataset of 250 000
date vectors.
Best, Felix
-----Ursprüngliche Nachricht-----
Von: David Winsemius [mailto:dwinsem...@comcast.net]
Gesendet: Dienstag, 3. April 2012 19:08
An: Fischer, Felix
Cc: r-help@r-project.org
Betreff: Re: [R] identify time span in date vector
On Apr 3, 2012, at 9:35 AM, Fischer, Felix wrote:
> 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 :(
>
which( dates[4:(length(dates))] -dates[1:(length(dates)-3)] <365 &
dates[3:(length(dates)-1)] -dates[1:(length(dates)-3)] > 90)
[1] 2 3
> Any ideas would be appreciated,
> Felix
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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David Winsemius, MD
West Hartford, CT
______________________________________________
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