Hello all,
Could someone help me with the time zones in understandable & practical way?
I got completely stucked with this.
Have googled for a while and read the manuals, but without solutions...
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When data imported from Excel 2007 into R (2.13)
all time variables, depending on date (summer or winter) get (un-asked for
it!) a time zone addition CEST (for summer dates) or CET (for winter dates).
> Dataset
Start End1 End2
days2End1.from.Excel days2End2.from.Excel
days2End1.in.R days2End2.in.R
1 2010-01-01 2011-01-01 2012-01-01
365 730
365 days 730.0000 days
2 2010-02-01 2011-02-01 2012-01-01
365 699
365 days 699.0000 days
3 2010-03-01 2011-03-01 2012-01-01
365 671
365 days 671.0000 days
4 2010-04-01 2011-04-01 2012-01-01
365 640
365 days 640.0417 days
5 2010-05-01 2011-05-01 2012-01-01
365 610
365 days 610.0417 days
6 2010-06-01 2011-06-01 2012-01-01
365 579
365 days 579.0417 days
7 2010-07-01 2011-07-01 2012-01-01
365 549
365 days 549.0417 days
8 2010-08-01 2011-08-01 2012-01-01
365 518
365 days 518.0417 days
9 2010-09-01 2011-09-01 2012-01-01
365 487
365 days 487.0417 days
10 2010-10-01 2011-10-01 2012-01-01
365 457
365 days 457.0417 days
11 2010-11-01 2011-11-01 2012-01-01
365 426
365 days 426.0000 days
12 2010-12-01 2011-12-01 2012-01-01
365 396
365 days 396.0000 days
> Dataset$Start
[1] "2010-01-01 CET" "2010-02-01 CET" "2010-03-01 CET" "2010-04-01 CEST"
"2010-05-01 CEST" "2010-06-01 CEST" "2010-07-01 CEST" "2010-08-01 CEST"
"2010-09-01 CEST" "2010-10-01 CEST" "2010-11-01 CET" "2010-12-01 CET"
> Dataset$End1
[1] "2011-01-01 CET" "2011-02-01 CET" "2011-03-01 CET" "2011-04-01 CEST"
"2011-05-01 CEST" "2011-06-01 CEST" "2011-07-01 CEST" "2011-08-01 CEST"
"2011-09-01 CEST" "2011-10-01 CEST" "2011-11-01 CET" "2011-12-01 CET"
> Dataset$End2
[1] "2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET"
"2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET"
"2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET" "2012-01-01 CET"
Variables 'days2End1.from.Excel and 'days2End2.from.Excel' are calculated
in Excel.
Same calculation (with same outcome!) I would like to be able to perform
with R.
Variables 'days2End1.in.R' and 'days2End2.in.R are calculated with R.
> Dataset$days2End1.from.Excel
[1] 365 365 365 365 365 365 365 365 365 365 365 365
> Dataset$days2End1.in.R <- with(Dataset, End1- Start)
> Dataset$days2End1.in.R
Time differences in days
[1] 365 365 365 365 365 365 365 365 365 365 365 365
attr(,"tzone")
[1] ""
> Dataset$days2End2.from.Excel
[1] 730 699 671 640 610 579 549 518 487 457 426 396
> Dataset$days2End2.in.R <- with(Dataset, End2- Start)
> Dataset$days2End2.in.R
Time differences in days
[1] 730.0000 699.0000 671.0000 640.0417 610.0417 579.0417 549.0417 518.0417
487.0417 457.0417 426.0000 396.0000
attr(,"tzone")
[1] ""
Quastion 1:
As you can see 'Dataset$days2End2.in.R' gives wrong 'day' calculation at
time period April until October, when CEST (summer) times are recorded
640.0417 610.0417 579.0417 549.0417 518.0417 487.0417 457.0417
giving decimals on days, where round days expected (640 610 579 549 518 487
457).
Can someone explain me how to deal with it in R?
What is the best way to calculate days in R getting correct calculations?
Question 2:
As I only need to work with dates without time and without time zones, I
would be happy to remove them if possible.
I tried already the trunc() function but without succes. The result doesn't
change.
> Dataset$days2End2.in.R.TRUNC <- with(Dataset, trunc(End2)- trunc(Start))
> Dataset$days2End2.in.R.TRUNC
Time differences in days
[1] 730.0000 699.0000 671.0000 640.0417 610.0417 579.0417 549.0417 518.0417
487.0417 457.0417 426.0000 396.0000
attr(,"tzone")
[1] ""
I would be happy if someone could light up this thing.
Many thanks in advance!
Laura
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