system.time
CPU Time Used

### Description

Calculates the CPU time that "expr" uses.

### Usage

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

### Arguments

expr | an expression that takes CPU time.
gcFirst | a logical value. If TRUE (the default), specifies that garbage collection occurs before timing "expr".

### Details

if "expr" is omitted, system.time retrieves the CPU usage time and shows the error condition. If any child processes are spawned during the current session, system.time cumulates them to user and system times.
Value
returns a numeric vector of class proc_time, identified by:

- "user.self"
- "sys.self"
- "elapsed"
- "user.child"
- "sys.child"

giving the user, system, and elapsed times for the currently running engine process, in units of seconds.
The print and summary methods for proc_time add the child times to the corresponding self times and labels them "user", "system", and "elapsed".
See Also
proc.time
Examples

    timeLinearAlgebra <- function(n)
    {
        MatA <- matrix(log2(seq_len(29*31)), nrow=29, ncol=31)
        MatB <- matrix(seq_len(31*37), nrow=31, ncol=37)
        # elapsed less than user+system on multicore machine
        system.time(for(i in seq_len(n)) MatA %*% MatB)
    }
    timeLinearAlgebra(10000)
    timeFileAccess <- function(n)
    {
        tf <- tempfile()
        on.exit(unlink(tf))
        # lots of system time, lots more elapsed time
        system.time(for(i in seq_len(n))cat(file=tf, i, "\n", sep=""))
    }
    timeFileAccess(5000)

Package base version 6.1.5-18
Package Index