[R] Minutes after midnight to time

[Jeff Newmiller]

On Fri, 13 Dec 2013, Trevor Davies wrote:

> Is there a quick function that can convert minutes (seconds) after midnight
> to a time?
>
> i.e 670.93 (minutes after midnight) --> 11:10:56.**
>
> I know it can be done by hand but I thought there must be a function for
> this already.

Sort of.  There isn't really a "time-of-day" datatype in R in the way you 
are thinking about it, so naturally there are no functions associated with 
that data type. (This is actually how Excel does it also.) There is the 
difftime data type, but it does not print to your desired format.

However, you can ignore the date portion of a POSIXt type:

strftime( as.POSIXct( "1970-01-01" ) + as.difftime( 670.93, units="mins" 
), "%H:%M:%OS3" )

[1] "11:10:55.799"

However, this is not a particularly computationally efficient route to 
your goal (a large vector of minutes values converts quickly to difftime, 
and that adds quickly to the POSIXct value, but then strftime converts it 
to POSIXlt for putting pieces into the string which is not so "quick"), so 
if you are looking for "quick" execution you might want to go ahead and do 
it, as you say, "by hand".

On the other hand, I find it quite "quick" to remember how to do this, so 
in that sense it could be described as "quick".

> Thank you.
>
> 	[[alternative HTML version deleted]]

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