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).
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.
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