Special operators (%in%, %*%) in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the %in% operator do in R?

The %in% operator checks if elements of one vector are present in another vector. It returns a logical vector of TRUE or FALSE values.

beginner

How does the %*% operator work in R?

The %*% operator performs matrix multiplication between two matrices or vectors, following the rules of linear algebra.

beginner

Example: What is the result of c(1, 2, 3) %in% c(2, 3, 4)?

The result is a logical vector: FALSE TRUE TRUE. It shows which elements of the first vector are found in the second.

intermediate

Example: What is the output of matrix(c(1,2,3,4), nrow=2) %*% matrix(c(5,6,7,8), nrow=2)?

The output is a 2x2 matrix: [,1] [,2] [1,] 19 22 [2,] 43 50 This is the result of multiplying the two matrices using matrix multiplication rules.

intermediate

Can %in% be used with data frames or lists?

Yes, %in% can be used to check if elements exist in vectors extracted from data frames or lists, but it works element-wise on vectors, not directly on data frames.

What does the expression '3 %in% c(1, 2, 3, 4)' return in R?

A TRUE

B FALSE

C 3

D Error

3 is present in the vector c(1, 2, 3, 4), so %in% returns TRUE.

Which operator is used for matrix multiplication in R?

A *

B %*%

C %in%

D %%

The %*% operator performs matrix multiplication in R.

What is the output type of 'c(1,2,3) %in% c(2,3,4)'?

A Numeric vector

B Matrix

C Logical vector

D Character vector

%in% returns a logical vector indicating presence or absence.

If A is a 2x3 matrix and B is a 3x2 matrix, what does A %*% B produce?

A Error

B A 3x3 matrix

C A 2x3 matrix

D A 2x2 matrix

Matrix multiplication of 2x3 and 3x2 matrices results in a 2x2 matrix.

Can %in% be used to check if a value is in a list directly?

A No, it only works on vectors

B Yes, it works directly on lists

C Yes, but only for numeric lists

D No, it only works on matrices

%in% works element-wise on vectors, not directly on lists.

Explain how the %in% operator works and give a simple example.

Think about checking if items are inside a shopping list.

Describe the purpose of the %*% operator and what kind of data it works with.

Imagine multiplying two tables of numbers to get a new table.