Hi,
I'm newish to R, a recent convert from Matlab... So far I'm impressed, and
determined to solve the following problem, which seems like it should be
easy:
I have a long (millions of points) data series recorded with a datalogger
that produced a timestamp in 4 columns: Year, Day of Year, Time in (H)HMM
and Seconds. I would like to have R interpret these columns as a time
object and have made some progress (e.g., using paste() to create a single
column and then strptime() to interpret -- is that too roundabout??), but
one thing is throwing me off and I can't seem to conquer it. The
hour-minute column in the raw data has no colon, so noon looks like "1200".
Morning times have only 3 characters and afternoon times have 4. I've been
playing around with a fake set of times:
times <- c(110, 230, 459, 1001, 1238, 1922)
When I use
strptime(data, "%k%M")
the last three are interpreted fine but the first three are messed up
because, for some reason, (even though I use %k for hour format?) the first
two characters are assumed to be hour and the remaining one is minutes. For
times[3] I get NA because R doesn't know what to do with 45 hours...
[1] "2010-06-03 11:00:00" "2010-06-03 23:00:00" NA
[4] "2010-06-03 10:01:00" "2010-06-03 12:38:00" "2010-06-03 19:22:00"
Fair enough, so I tried a different angle, using an if...else statement:
hours <- if(nchar(times)>3) strtrim(times,2) else strtrim(times,1)
This worked great when times was only a vector of length=1, but when I try
to apply it to something larger, I get the following warning:
Warning message:
In if(nchar(times)>3) strtrim(times,2) else strtrim(times,1) :
the condition has length > 1 and only the first element will be used
and the output hours are only the first character. Not entirely sure if I
understand this.
Any advice on how to do this? Are there packages or commands that I'm not
aware of that know how to deal with (h)hmm times?
Thanks much,
-Pete
---------------------------------------------
platform i486-pc-linux-gnu
arch i486
os linux-gnu
system i486, linux-gnu
status
major 2
minor 10.1
year 2009
month 12
day 14
svn rev 50720
language R
version.string R version 2.10.1 (2009-12-14)
--
Pete Moore
Postdoctoral Research Associate
Dept. Geological & Atmospheric Sciences
Iowa State University
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