Functions
In R, the operations that do all the work are called functions. We’ve already used a few functions above (you can’t do anything interesting in R without them). Functions are just like what you remember from math class. Most functions are in the following form:
f(argument1, argument2, ...)
Where f
is the name of the
function, and argument1
, argument2
, . . . are the arguments to the function. Here are a few more examples:
> exp(1) [1] 2.718282 > cos(3.141593) [1] -1 > log2(1) [1] 0
In each of these examples, the functions took only one argument. Many functions require more than one argument. You can specify the arguments by name:
> log(x=64, base=4)
[1] 3
Or, if you give the arguments in the default order, you can omit the names:
> log(64,4)
[1] 3
Not all functions are of the form f(...)
. Some of them are in the form of
operators.[7] For example, we used the addition operator (“+”) above. Here
are a few examples of operators:
> 17 + 2 [1] 19 > 2 ^ 10 [1] 1024 > 3 == 4 [1] FALSE
We’ve seen the first one already: it’s just addition. The second
operator is the exponentiation operator, which is interesting because it’s
not a commutative operator. The third operator is the equality operator.
(Notice that the result returned is FALSE
; R has a Boolean data type.)
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