system.time {base}R Documentation

CPU Time Used


Return CPU (and other) times that expr used.


system.time(expr, gcFirst = TRUE)
unix.time(expr, gcFirst = TRUE)


expr Valid R expression to be “timed”
gcFirst Logical - should a garbage collection be performed immediately before the timing? Default is TRUE.


system.time calls the function proc.time, evaluates expr, and then calls proc.time once more, returning the difference between the two proc.time calls.

unix.time is an alias of system.time, for compatibility with S.

Timings of evaluations of the same expression can vary considerably depending on whether the evaluation triggers a garbage collection. When gcFirst is TRUE a garbage collection (gc) will be performed immediately before the evaluation of expr. This will usually produce more consistent timings.


A object of class "proc_time": see proc.time for details.


It is possible to compile R without support for system.time, when the function will throw an error.

See Also

proc.time, time which is for time series.


system.time(for(i in 1:100) mad(runif(1000)))
## Not run: 
exT <- function(n = 1000) {
  # Purpose: Test if system.time works ok;   n: loop size
  system.time(for(i in 1:n) x <- mean(rt(1000, df=4)))
#-- Try to interrupt one of the following (using Ctrl-C / Escape):
exT()                 #- about 3 secs on a 1GHz PIII
system.time(exT())    #~ +/- same
## End(Not run)

[Package base version 2.5.0 Index]