Operators in R

R's binary and logical operators will look very familiar to programmers. Note that binary operators work on vectors and matrices as well as scalars.

Arithmetic Operators

Logical Operators

# An example
x <- c(1:10)
x[(x>8) | (x<5)]
# yields 1 2 3 4 9 10

# How it works
x <- c(1:10)
x
1 2 3 4 5 6 7 8 9 10
x > 8
F F F F F F F F T T
x < 5
T T T T F F F F F F
x > 8 | x < 5
T T T T F F F F T T
x[c(T,T,T,T,F,F,F,F,T,T)]
1 2 3 4 9 10

Tips for Using Operators in R

Operators play a pivotal role in R programming, allowing for a wide range of operations from basic arithmetic to complex logical evaluations. Here are some tips to ensure you use them effectively and avoid common pitfalls:

1. Be Mindful of Operator Precedence

Just like in mathematics, operators in R have a hierarchy of precedence. For instance, multiplication and division are performed before addition and subtraction. Use parentheses to ensure the desired order of operations.

2. Use Spaces for Clarity

While x+y and x + y are functionally identical, the latter is easier to read. Use spaces around operators to enhance code readability.

3. Double Check == and =

In R, == is a logical operator for comparison, while = can be used for assignment (though <- is more conventional). Ensure you're using the right one for the right task.

4. Avoid Common Pitfalls with Logical Operators

Remember that & and | are element-wise logical operators, while && and || evaluate the first element of a vector and are often used in control structures.

5. Use %in% for Vector Membership

Instead of using multiple OR conditions, you can use the %in% operator to check if an element belongs to a vector or list. For example, x %in% c(1, 2, 3) is more concise than x == 1 | x == 2 | x == 3.

6. Beware of Floating Point Comparisons

Due to the way computers handle floating-point arithmetic, direct comparisons can sometimes yield unexpected results. Instead of x == 0.3, consider using all.equal(x, 0.3) or check if the difference is below a small threshold.

7. Use identical() for Exact Comparisons

When you want to check if two objects are exactly the same, use the identical() function. It's more stringent than == and avoids potential pitfalls with factors or attributes.

8. Remember the Global Assignment Operator <<-

While <- is the standard assignment operator, <<- assigns values globally, even outside the current function or environment. Use it judiciously.

9. Explore Special Operators

R has a rich set of special operators like %/% for integer division or %% for modulus. Familiarize yourself with these to expand your coding toolkit.

10. Stay Updated

R is an evolving language. Stay updated with the latest versions and changes, as new operators or functionalities might be introduced.

By keeping these tips in mind and practicing regularly, you'll be able to harness the full power of operators in R, making your code more efficient, readable, and robust. 

Going Further

To practice working with logical operators in R, try the free first chapter on conditionals of this interactive course.

This content is taken from statmethods.net.