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One situation in which you can really get into trouble is when you use capital F or T as an object name. You can do it, but you’re likely to break code at some point. Although it’s a very bad idea, T and F are all too often used as abbreviations for TRUE and FALSE, respectively. But T and F are not reserved keywords. So, if you change them, R will first look for the object T and only then try to replace T with TRUE. And any code that still expects T to mean TRUE will fail from this point on. Never use F or T, not as an object name and not as an abbreviation.

Choosing a naming style

      If you have experience in programming, you’ve probably heard of camel case before. Camel case is a way of giving longer names to objects and functions. You capitalize every first letter of a word that is part of the name to improve the readability. So, you can have a veryLongVariableName and still be able to read it.

      Unlike many other languages, R doesn’t use the dot (.) as an operator, so the dot can be used in names for objects as well. This style is called dotted style, where you write everything in lowercase and separate words or terms in a name with a dot. In fact, in R, many function names use dotted style. You’ve met a function like this earlier in the chapter: print.default(). Some package authors also use an underscore instead of a dot.

      

print.default() is the default method for the print() function. You can find Information on the arguments of the Help page for print.default().

      You’re not obligated to use dotted style; you can use whatever style you want. We use dotted style throughout this book for objects, and camel case for functions. R uses dotted style for many base functions and objects, but because some parts of the internal mechanisms of R rely on that dot, you’re safer using camel case for functions. Whenever you see a dot, though, you don’t have to wonder what it does – it’s just part of the name.

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