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


Operator	Description
+	addition
-	subtraction
*	multiplication
/	division
^ or **	exponentiation
x %% y	modulus (x mod y) 5%%2 is 1
x %/% y	integer division 5%/%2 is 2

Logical Operators


Operator	Description
<	less than
<=	less than or equal to
>	greater than
>=	greater than or equal to
==	exactly equal to
!=	not equal to
!x	Not x
**x	y**
x & y	x AND y
isTRUE(x)	test if X is TRUE

# 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:

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.

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.

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.

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.

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.

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.

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.

Remember the Global Assignment Operator <<-:

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

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.

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.

Frequently Asked Questions (FAQ) about Operators in R

What's the difference between <- and = for assignment in R?

Both <- and = can be used for assignment in R. However, <- is the more traditional and preferred way, especially in scripts and functions. The = operator is often used within function calls to specify named arguments.

Why does 1/3 == 0.3333333 return FALSE in R?

This is due to the way computers handle floating-point arithmetic. Direct comparisons of floating-point numbers can lead to unexpected results because of precision limitations. Instead, consider using all.equal(1/3, 0.3333333) or check if the difference is below a small threshold.

Can I use && and || for vectorized logical operations?

No, && and || are not vectorized. They evaluate only the first element of a vector. For element-wise logical operations on vectors, use & (AND) and | (OR).

How do I check if an element is in a vector or list?

Use the %in% operator. For example, to check if x is in the vector c(1, 2, 3), you'd use x %in% c(1, 2, 3).

What does the %% operator do?

The %% operator returns the modulus (remainder) of a division operation. For instance, 5 %% 2 would return 1, as the remainder of 5 divided by 2 is 1.

How can I perform integer division in R?

Use the %/% operator. For example, 5 %/% 2 returns 2, as 5 divided by 2 yields a quotient of 2.

Why does 2 == "2" return TRUE?

R performs type coercion in certain situations. In this case, it's converting the character "2" to a numeric value for the comparison. However, relying on this behavior can lead to unexpected results. It's always best to ensure data types match before making comparisons.

How do I assign a value globally from within a function?

Use the <<- operator. This assigns the value globally, even outside the current function or environment. However, be cautious with its use, as it can lead to unexpected side effects.

Can I create custom operators in R?

Yes, R allows for the creation of custom infix operators. These operators must start and end with the percentage symbol (%). For example, %myop%. You can then define its behavior like any other function.

How do I ensure exact comparisons between two objects in R?

Use the identical() function. It checks if two objects are exactly the same, considering factors, attributes, and other nuances that == might overlook.

Going Further

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