[R] Mystified - comparing chron times

B77S bps0002 at auburn.edu
Fri Sep 16 16:08:43 CEST 2011

I'm sure Sarah's solution works (and she knows more about R than myself), but
I ran into a similar problem and used:

good luck regardless.


Sarah Goslee wrote:
> Sounds like a case for FAQ 7.31, or, yet another machine precision issue.
> Try all.equal() instead of ==
> Sarah
> On Fri, Sep 16, 2011 at 7:36 AM, mebstyne <mebstyne at me.com> wrote:
>> I have two local variables: startTime and expectedStartTime.  Both are
>> chron
>> related objects.
>> When I look at the class for the objects I can see they are of class
>> "times".
>> When I print them to the console, they both read: "09:30:00"
>> When I print them as.numeric(), they both read: 0.3958333
>> When I try and compare them: (as.numeric(startTime) ==
>> as.numeric(expectedStartTime)) it returns FALSE.
>> I'm mystified.  I would expect them to be true.
>> Perhaps a key to the riddle is how the two objects were created.
>> "startTime" was created by reading a text field from a socket, converting
>> it
>> into a chron object using chron(x, "%m/$d/%Y %H:%M:%S"), then finally I
>> created a time out of the chron by doing a quick butchering of the
>> "integer"
>> portion of the numeric: (times(as.numeric(x) - as.integer(x))
>> "expectedStartTime" was created by the command times('09:30:00')
>> Any suggestions?  Tips?  Alternative approaches?  I've pulled too many
>> hairs
>> triaging this.
>> All hands welcomed on this little challenge.
>> Big picture goal of what I'm doing: I have a list of chron objects with
>> both
>> dates and times portion filled out and I'm trying to determine if the
>> time
>> is a specific time (specific to the minute).
>> Thanks!
>> -Michael
> -- 
> Sarah Goslee
> http://www.functionaldiversity.org
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