[R] Help with POSIX

Jeff Newmiller jdnewmil at dcn.davis.CA.us
Tue Mar 31 04:11:53 CEST 2015

You seem to be trying to make POSIXt into something it isn't, as though this was Excel. 

First, POSIXt is not the same as numeric. You can convert between them, but they are not the same. If you want to do numeric operations, convert.

Second, POSIXt is not time of day only. When you provide only minutes and seconds to strptime, it includes the current date in the result as well. Thus, values converted today will be different than values converted tomorrow. You should probably pick a specific date to include in every "time" value, and paste it with the actual data before converting.

Finally, formatting of all non-character data is always associated with conversion to character. You either need to reconvert on demand or keep a copy of the data around unconverted for use when you need it.

Oh, and your use of HTML is leading to corruption of your code. Learn to use your email program so you don't send us garbage to guess at.
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On March 30, 2015 6:15:09 PM PDT, "Doran, Harold" <HDoran at air.org> wrote:
>I�m struggling a bit with learning about POSIX objects to do some basic
>things with objects of this class. Suppose I have the following simple
>times <- c("03:20", "29:56", "03:30", "21:03", "56:26")
>aa <- strptime(times, "%M:%S�)
>I can do means, and some other basic things, but I cannot correlate the
>objects with some other variable
>cor(aa, rnorm(5))
>Also, for purposes of a user-interface I have built with shiny, I need
>for the time to be viewed as simply as minutes:seconds, such as this
>format(aa, '%M:%S�)
>But of course after doing this I lose the ability to work with this
>object as a time variable.
>Thank you
>	[[alternative HTML version deleted]]
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