system.time

R Base 3.6.2

Return CPU (and other) times that expr used.

Syntax

system.time(expr, gcFirst = TRUE)
<!-- %Deprecated unix.time(expr, gcFirst = TRUE) -->

Arguments

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

Return Value

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

Details

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 has been an alias of system.time, for compatibility with S, and has finally been deprecated in 2016. 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.

Examples

Example

# NOT RUN {
require(stats)
# }
# NOT RUN {
system.time(for(i in 1:100) mad(runif(1000)))
# }
# NOT RUN {
exT <- function(n = 10000) {
  # 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 4 secs on a 2.5GHz Xeon
system.time(exT())    #~ +/- same
# }