[R] R treating time

[Michal Kulich]

There is an alternative through strsplit() when the desired output format is numeric (fractional hours on 0-24 scale).

> aa <- c("3:00","11:42")
> bb <- strsplit(aa,":")
> bb
[[1]]
[1] "3"  "00"

[[2]]
[1] "11" "42"

> cc <- sapply(bb,function(x){as.numeric(x[1])+as.numeric(x[2])/60})
> cc
[1]  3.0 11.7

AM/PM can be dealt with similarly.

> aa <- c("3:00pm","11:42am")
> pm <- grepl("pm",aa)
> pm
[1]  TRUE FALSE
> bb <- strsplit(sub("[ap]m$","",aa),":")
> bb
[[1]]
[1] "3"  "00"

[[2]]
[1] "11" "42"

> cc <- sapply(bb,function(x){as.numeric(x[1])+as.numeric(x[2])/60})+12*pm
> cc
[1] 15.0 11.7

Cheers,

M. Kulich



On 7.1.2010 8:26, Dennis Murphy wrote:
> Hi:
> 
> Let
> x <- '3:00'
> 
> The R package for data that are only dates or only times is chron. For
> times,
> it appears that the strings need to be in the form hh:mm:ss on a 24-hour
> clock, so for
> example, 1:30 PM should be expressed as 13:30:00. [I didn't see any option
> for a
> 12-hour clock with an optional argument to designate AM or PM...if wrong,
> I'm
> sure I'll be corrected...]
> 
> 
> Using the x value above, we have
> 
>> library(chron)
>> times(x)
>> x <- '3:00'
>> times(x)
> Error in convert.times(times., fmt) : format h:m:s may be incorrect
> In addition: Warning messages:
> 1: In unpaste(times, sep = fmt$sep, fnames = fmt$periods, nfields = 3) :
>   wrong number of fields in entry(ies) 1
> 2: In convert.times(times., fmt) : NAs introduced by coercion
> 3: In convert.times(times., fmt) : NAs introduced by coercion
> 4: In convert.times(times., fmt) : NAs introduced by coercion
> 
> So '3:00' isn't enough; we need to add on some seconds...
> 
>> x <- paste(x, ':00', sep = '')
>> x
> [1] "3:00:00"
>> times(x)                             # Now it works.
> [1] 03:00:00
> 
> To show you that this works equally well with vectors, suppose the
> input times were a vector
> z <- c('3:00', '4:15', '12:25', '16:41')
> 
> # Use the same trick as above (paste() is also vectorized)..
> z <- paste(z, ':00', sep = '')
> times(z)
> # [1] 03:00:00 04:15:00 12:25:00 16:41:00
> 
> 
> Consult ?chron and the examples contained within. You can run the
> examples on the help page with example(chron).
> 
> HTH,
> Dennis
> 
> 
> On Wed, Jan 6, 2010 at 9:32 PM, chrisli1223 <chrisli at austwaterenv.com.au>wrote:
> 
>>
>> Hi all,
>>
>> I have imported a value 3:00 from Excel into R using read.csv. I want R to
>> recognise it as 3:00am (time data). How do I do it?
>>
>> Thanks in advance,
>> Chris
>> --
>> View this message in context:
>> http://n4.nabble.com/R-treating-time-tp1008608p1008608.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
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>>
> 
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> 
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-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Michal Kulich, PhD
Dept. of Probability and Statistics
Charles University
Sokolovska 83
186 75 Praha 8
Czech Republic

Phone  +420-221-913-229
Fax:   +420-283-073-341, +420-222-323-316
Email: kulich at karlin.mff.cuni.cz