R - How to get the time elapsed between two points? - r

Question

I've tried to use Sys.time to get the time elapsed between two points. However, it doesn't output in a way I like.
This is how it looks now:
a <- Sys.time
...running stuff between these two points...
b <- Sys.time
c <- b - a
c
Time difference of 1.00558 hours
I only want the number and the units. I know that to get just the number I can do:
c[[1]]
However, sometimes the result of c can give me seconds or minutes. I only want instances wherein I have the number and when the units are in hours. Does anyone know of a way such that I would get something like the following, using Sys.time() (or any alternative):
if (units == "hours")
{
if (number => 1)
{
#do something
}
}

Answer 1

Using difftime of base R allows you to obtain the time difference in different units. Rest is formatting.
a = Sys.time()
Sys.sleep(5) #do something
b = Sys.time()
paste0(round(as.numeric(difftime(time1 = b, time2 = a, units = "secs")), 3), " Seconds")
#[1] "5.091 Seconds"

Answer 2

The package tictoc simplifies this kind of timing. It doesn't return hours, but we can create a new function that converts its second-based measurements into hours.
library(tictoc)
toc_hour <- function() {
x <- toc()
(x$toc - x$tic) / 3600
}
You normally start the timer with tic() and stop it with toc().
tic()
Sys.sleep(2)
toc()
# 2.02 sec elapsed
Calling toc_hour() instead of toc() returns the number of hours that have elapsed.
tic()
Sys.sleep(2)
toc_hour()
# 2.25 sec elapsed
# elapsed
# 0.000625
It still prints the number of seconds above the hours, but if you capture the result it will only store the number of hours for downstream analysis.
tic()
Sys.sleep(2)
x <- toc_hour()
if(x < 1) {print("This took under an hour")}

Answer 3

You can evaluate everything as an argument to the system.time function. It will give you the elapsed time in seconds.
paste0(system.time( rnorm(1000000, 0, 1) )[3] / 3600, " hours")
# "2.58333333334172e-05 hours"
Alternatively, you can use Frank's suggestion in the comments. difftime(b, a, units = "hours") which is probably the dominant solution in most cases

Answer 4

The tictoc package normally returns seconds. The other solutions from this package manually converts this to other units but I find it still doesn't look right. Instead, use the built-in func.toc argument in toc() to change the output. For example:
toc_min <- function(tic,toc,msg="") {
mins <- round((((toc-tic)/60)),2)
outmsg <- paste0(mins, " minutes elapsed")
}
And then:
tic()
Sys.sleep(1)
toc(func.toc=toc_min)
returns
0.02 minutes elapsed

Answer 5

I think lubridate is the quickest solution for you:
start <- Sys.time()
## Do Stuff here
end <- Sys.time()
elapsed <- lubridate::ymd_hms(end) - lubridate::ymd_hms(start)
message(elapsed)
It should return something useful like:
"Time difference of 12.1 hours"

Answer 6

Maybe you can try the ´tictoc´ package.
As described in the documentation you can do the following:
tic()
#Do something
toc(log = TRUE, quiet = TRUE)
#Put the result in a log
log.txt <- tic.log(format = TRUE)
#Extract only the value
res <- gsub( " sec elapsed", "", unlist(log.txt))
#Clear the log
tic.clearlog()
That way, res gives you only the value and is in seconds, so it is pretty simple to have hours then.
Moreover, if you don't clear the log you can put successions of tic() and toc() and put everything in your log.txt, and then gsub( " sec elapsed", "", unlist(log.txt)) will give you a vector of strings with the value in seconds for each iteration which can be pretty useful