10.4 Getting help

The help() function is special in that it provides information about other functions. This function displays a help page, which is online documentation that describes what a function does. This includes an explanation of all of the arguments to the function and a description of the result produced by the function. Figure 10.1 shows the beginning of the help page for the Sys.sleep() function, which is obtained by typing help(Sys.sleep).

**Figure 10.1:** The beginning of the help page for the function `Sys.sleep()` as displayed within an xterm on a Linux system. This help page is displayed by the expression `help(Sys.sleep)`.
Sys.sleep package:base R Documentation Suspend Execution for a Time Interval Description: Suspend execution of R expressions for a given number of seconds Usage: Sys.sleep(time) Arguments: time: The time interval to suspend execution for, in seconds. Details: Using this function allows R to be given very low priority and hence not to interfere with more important foreground tasks. A typical use is to allow a process launched from R to set itself up and read its input files before R execution is resumed.

Sys.sleep                package:base            R Documentation

Suspend Execution for a Time Interval

Description:

     Suspend execution of R expressions for a given number of 
     seconds

Usage:

     Sys.sleep(time)

Arguments:

    time: The time interval to suspend execution for, in seconds.

Details:

     Using this function allows R to be given very low priority 
     and hence not to interfere with more important foreground 
     tasks. A typical use is to allow a process launched from R 
     to set itself up and read its input files before R execution 
     is resumed.

A special shorthand using the question mark character, ?, is provided for getting the help page for a function. Instead of typing help(Sys.sleep), it is also possible to simply type ?Sys.sleep.

There is also a web interface to the help system, which is initiated by typing help.start().

Many help pages also have a set of examples to demonstrate the proper use of the function, and these examples can be run using the example() function.