Page 48 - Applied Statistics Using SPSS, STATISTICA, MATLAB and R

1.8 Software Tools 27

Figure 1.12. An illustration of R on-line help of function mean. The “Help on
‘mean’” is displayed in a specific window.

An R data frame is a recipient for a list of objects. We mostly use data frames
that are simply data matrices with appropriate column names, as in the above
matrix m .
Operations on data are obtained by using suitable R functions. For instance,

> mean(x)
[1] 3.5

displays the mean value of the x vector on the console. Of course one could also
assign this mean value to a new variable, say mu , by issuing the command
mu <- mean(x) .
Whenever needed one may obtain the information on which objects are
currently in the console environment by using ls()(“list”). (Be sure to include the
parentheses; otherwise R will interpret it as you wishing to obtain the ls function
code.) Object removal is performed by applying the function rm (“remove”) to a
list of object identifiers. For instance, rm(x) removes matrix x from the
environment; it will no longer be available.
On-line help about general topics of R, namely command constructs and
available functions, can be obtained from the Help menu option of the R Gui. On-
line help about a specific function can be obtained using the R help function as
illustrated in Figure 1.12.