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


     Suspend execution of R expressions for a given number of 




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


     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.

Paul Murrell

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