You haven't given us the 'at a minimum' information that the posting guide
requested, so we don't know your timezone. But in America/Toronto on my
F8 machine
d <- "2007-11-04 01:30:00"
dd <- as.POSIXct(d)
c(dd, dd+3600)
[1] "2007-11-04 01:30:00 EDT" "2007-11-04 01:30:00 EST"
Note the change of timezone. Wikipedia says that is the right day for
Canada ('from 2:00 a.m. LDT to 1:00 LST on the first Sunday in November
since 2007'). Note that 01:34 is ambiguous that day (see ?as.POSIXct,
surely part of the required homework).
The N American late change in rules in 2007 means that DST changes can be
unreliable in OSes, but this one seems to be correct.
I do believe that you have failed to credit the careful work in getting
this right in R. Perhaps these are not times in Ontario and you forgot to
tell R that?
On Thu, 14 Aug 2008, Bill Szkotnicki wrote:
Hi,
I am computing some time differences.
Using the linux version of R 2.7.1
And I am getting a strange result ( see below )
I need the difference in minutes.
Actually looking for where it is NOT 15 minutes.
Would anyone know why this could be happening?
Or should I do this another way?
Bill
The script "k0.R"
===============
a=read.table("buzwah005.txt")
d=strptime(paste(a[,1]," ",a[,2]),"%m/%d/%Y %H:%M")
tm=-24*60*as.numeric(as.POSIXlt("2007-1-1")-d) # time since midnight Jan 1
print(tm[2]-tm[1])
x=a[,3]
diffs=round(tm[-1]-tm[-length(tm)])
not15=(1:length(diffs))[diffs!=15]
print(not15)
===============
The R session....
source("k0.R")
[1] 15
[1] 2113 5686 15712
class(d)
[1] "POSIXt" "POSIXlt"
d[15711:15714]
[1] "2007-11-04 01:34:00" "2007-11-04 01:49:00" "2007-11-04 02:04:00"
[4] "2007-11-04 02:19:00"
d[15712]-d[15711]
Time difference of 15 mins
d[15713]-d[15712]
Time difference of 1.25 hours
d[15714]-d[15713]
Time difference of 15 mins
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--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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and provide commented, minimal, self-contained, reproducible code.
