Data file handbook by International Business Machines Corporation. Data Processing

By International Business Machines Corporation. Data Processing Division

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To list the names of existing variables, use the function ls. This is named after the equivalent Unix command, and follows the same convention: by default, variable names that begin with a . are hidden. str. This is, as you might expect, a combination of the ls and str functions, and is very useful during debugging sessions (see “Debugging” on page 292 in Chap‐ ter 16). info After working for a while, especially while exploring data, our workspace can become quite cluttered. We can clean it up by using the rm function to remove variables: rm(peach, plum, pear) rm(list = ls()) #Removes everything.

Chapter Goals After reading this chapter, you should: • Know what a class is, and the names of some common classes • Know how to convert a variable from one type to another • Be able to inspect variables to find useful information about them • Be able to manipulate the user workspace Classes All variables in R have a class, which tells you what kinds of variables they are. For example, most numbers have class numeric (see the next section for the other types), and logical values have class logical.

9916 fac a:6 b:7 c:5 d:9 e:3 bool Mode :logical FALSE:12 TRUE :11 NA's :7 Similarly, the str function shows the object’s structure. 2796 ... frame': 30 obs. 2796 ... : 2 4 4 2 1 1 4 2 1 4 ... ## $ bool: logi NA FALSE FALSE TRUE TRUE TRUE ... As mentioned previously, each class typically has its own print method that controls how it is displayed to the console. Sometimes this printing obscures its internal struc‐ ture, or omits useful information. The unclass function can be used to bypass this, letting you see how a variable is constructed.

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