[R] Creating appropriate time axis for data

Jeff Newmiller jdnewmil at dcn.davis.ca.us
Tue Dec 13 13:23:43 CET 2011

"Does not support natively" isn't accurate. It is common to import date/time values as character and then use strptime or as.Date or other conversion function as desired. This may at first seem tedious, but it does provide flexibility.
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Tony Stocker <tonystocker at mail.com> wrote:

>2011/12/12 Uwe Ligges <ligges at statistik.tu-dortmund.de>:
>> On 12.12.2011 17:44, Tony Stocker wrote:
>Sorry for the double post but the first message was held for so long
>that I figured there was a problem with the email address I was using
>so I unsubscribed that one and resubscribed the other one.
>>> Hello,
>>> I am dealing with data stored in a database as a 'time' object.  I
>>> export the data from the database to a text file and utilize the
>>> 'time_to_sec()'
>> I get
>>> time_to_sec
>> Error: object 'time_to_sec' not found
>> If it is in a package, please tell us which one you are referring to.
>The time_to_sec() function is inside the database (in this case
>MySQL).  I'm using it solely because R doesn't want to deal with the
>times as normally outputted (HH:MM:SS) because it sees them as a
>character object and not a numerical or time object.  By converting
>these time fields to seconds when I export them from the database I
>provide something that R can work with natively apparently.
>>> seconds.  However when I visualize the data in charts I do not want
>>> scale that runs from 25200-64800 seconds, but rather in the HH:MM:SS
>>> format.  Is there a relatively straight-forward and easy to use way
>>> do this?
>> Yes, e.g.:
>> t <- strptime(c("07:00:00", "18:00:00"), "%H:%M:%S")
>> y <- rnorm(2)
>> plot(t, x)
>Does this method supercede  the original y-axis label or supplement
>it?  Will the data be correctly located along the y-axis if it's in
>I thought I had looked at strptime() and it required day/date info to
>be listed not just time.  Based on your example I'm assuming that I
>was incorrect in that assumption.
>Thanks for this suggestion I'll give it a try with my data and see if
>it does what I'd like it to do.  I appreciate the help.
>> Uwe Ligges
>R-help at r-project.org mailing list
>PLEASE do read the posting guide
>and provide commented, minimal, self-contained, reproducible code.

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