[R] time segments intersection

[Gabor Grothendieck]

Assuming the first row is the comparison row convert
to Date class and calculate:

DF[] <- lapply(DF, as.Date, format = "%Y/%m/%d")
pmin(DF[[2]], DF[1, 2]) - pmax(DF[[1]], DF[1,1])

Please be explicit next time in formulating your queries
as requested in the last line of every message to r-help.

On Sat, Oct 4, 2008 at 6:13 PM, [Ricardo Rodriguez] Your XEN ICT Team
<webmaster at xen.net> wrote:
> Gabor Grothendieck wrote:
>>
>> Mark did not post his response so I don't know what it
>> is.
>
> This is Mark's proposal. Sorry, I was speaking about it as if posted to the
> list.
>
> # MAKE POSIXct OBJECTS FROM CHARACTER STRINGS
> temp1 <- as.POSIXct(strptime("2007-02-02","%Y-%m-%d"))
> temp2 <- as.POSIXct(strptime("2007-02-01","%Y-%m-%d"))
>
> # TEMP1 AND TEMP2 ARE SORT OF NUMBERS BUT EACH UNIT IS ONE
> # SECOND
>
> result <- difftime(temp1,temp2)
>
> # STILL NOT REALLY A NUMBER
> print(result)
> print(str(result))
>
> # MAKE IT A NUMBER
> numberresult <- unclass(result)
> attributes(numberresult) <- NULL
> print(numberresult)
>
>> How you do it may depend on your setup which was
>> not entirely clear from the question since it started out
>> as if the two series were the inputs and then seemed to be
>> assuming the time ranges were.
>>
>
> Ranges are the case study. I have a table with dates like these:
>
> startProject    endProject
> 2006/12/01    2007/05/31
> 2007/02/01    2008/12/31
> 2007/02/01    2008/12/31
> 2007/02/01    2008/12/31
> 2007/02/01    2008/12/31
> 2006/11/22    2009/12/30
> 2003/01/01    2006/07/31
> 2004/12/28    2007/12/27
> 2005/12/23    2006/12/30
> 2008/01/01    2010/12/31
> 2005/12/23    2008/12/30
> 2005/12/23    2008/12/30
>
> For each record, I  need the value for a new variable (let's call it
> timeInCommon) that stores a numeric value: the number days that each range
> startProject:endProject intersects with a third range, let's call it t1:t2.
>>
>> Here are a few possibilities assuming z1 and z2
>> from my prior post.  Depending on what you want
>> you may need to add 1.
>>
>> diff(range(time(merge(z1, z2, all = FALSE))))
>>
>> diff(range(intersect(time(z1), time(z2))))
>>
>> r1 <- range(time(z1))
>> r2 <- range(time(z2))
>> pmin(r1, r2)[2] - pmax(r1, r2)[1]
>>
>> The first one generalizes to N series immediately.  The
>> second does not but is slightly shorter (although abbreviation
>> of the first could get that one even shorter).  The last
>> reduces the series to time ranges and then operates on
>> those.
>>
>>
>
> The second option generates directly the required numeric value. 5 days if
> we use the time series coming with your first message. My problem now is how
> to use it to populate this new timeInCommon variable for all and each
> records.
>
> Thanks for your help,
>
> Ricardo
>
>
> --
> Ricardo Rodríguez
> Your XEN ICT Team
>
>