Matrices in R Programming

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The post is about matrices in R Programming Language. These questions are about basic concepts and will improve the understanding of R programming-related job interviews or educational examinations.

In R language, matrices are two-dimensional arrays that store elements of the same data type (numeric, character, logical, etc.). They are created using the matrix() function, which takes a vector of data and specifies the number of rows (nrow) and columns (ncol). Matrices support operations like addition (+), subtraction (-), element-wise multiplication (*), and matrix multiplication (%*%). Key functions include dim() for dimensions, t() for transpose, solve() for inverse, and diag() for diagonal elements. Matrices are widely used in linear algebra, statistics, and data manipulation in R

Question 1: Write the general format of Matrices in R Programming Language.

Answer: The general format of matrices in the R Programming Language is

Mymatrix <- matrix (vector, nrow = r , ncol = c , byrow = FALSE,
                    dimnames = list (char_vector_for_rowname, char_vector_for_colnames)
                   )
matrices in r programming language

Question 2: Explain what is transpose.

Answer: The transpose is used to re-shape data. Before performing any analysis, R language provides various methods such as the transpose method for reshaping a dataset. To transpose a matrix or a data frame t() function is used.

Question 3: What is the main difference between an Array and a Matrix?

Answer: A matrix in R language is always a two-dimensional rectangular data set as it has rows and columns. However, an array can be of any number of dimensions, while each dimension of an array is a matrix. For example, a $3\times3\times2$ array represents 2 matrices each of dimension $3\times3$.

Question 4: What are R matrices and R matrices functions?

As discussed earlier, a matrix is a two-dimensional rectangular data set. The matrices in the R Programming language can be created using vector input to the matrix() function. Also, a matrix is a collection of numbers or elements that are arranged into a fixed number of rows and columns. Usually, the numbers or elements of the matrix are the real numbers, therefore, the data elements must be of the same basic type. Two types of matrix functions can be used to perform different computations on matrices in R Programming:

  • apply()
  • apply()

Question 5: How many methods are available to use the matrices?

Answer: There are many methods to solve the matrices like adding, subtraction, negative, etc.

Question 6: What is the difference between matrix and data frames?

Answer: A data frame can contain different types of data but a matrix can contain only similar types of data.

Question 7: What is apply() function in R?

Answer: The apply() function in R returns a vector (or array or list of values) obtained by applying a function to the margins of an array or matrix. the general syntax of the apply() function in R language is:

apply(X, MARGIN, FUN, …)

A short description of the arguments for the apply() functions are

  • X is an array, including a matrix.
  • MARGIN is a vector giving the subscripts to which the function will be applied.
  • FUN is the function to be applied.
  • … is optional arguments to FUN

Question 8: What is the apply() family in R?

Answer: The apply() functions in the R language are a family of functions in the base R. The family of these functions allows the users to act on many chunks of data. A apply() function is a loop, but runs faster than loops and often requires less code. There are many different apply functions.

  • There is some aggregating function. They include mean, or the sum (includes return a number or scalar);
  • Other transforming or subsetting functions.
  • There are some vectorized functions. They return more complex structures like lists, vectors, matrices, and arrays.
  • One can perform operations with very few lines of code in apply().

Question 9: What is sapply() Function in R?

Answer: A Dimension Preserving Variant of “sapply” and “lapply”. The sapply is a user-friendly version. It is a wrapper of lapply. By default, sapply returns a vector, matrix, or array. The general syntax of sapply() and lapply() is

Sapply(X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)
Lapply(X, FUN, ...)

A short description related to arguments of the above functions are:

  • X is a vector or list to call sapply.
  • FUN is a function.
  • … is optional arguments to FUN.
  • simplify is a logical value that defines whether a result is been simplified to a vector or matrix if possible.
  • USE.NAMES is logical; if TRUE and if X is a character, use X as the name for the result unless it had names already.
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R Programming Quiz 19

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The Quiz is about R Programming Quiz with Answers. There are 20 multiple-choice questions covering different topics related to R Language Programming. Let us start with the R Programming Quiz now.

Online R Programming Quiz with Answers

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1. After installing and calling the httr library in R, which method should you use to update a resource?

 
 
 
 

2. What is the main reason for using the R language?

 
 
 
 

3. In R, what is the result of the function as.numeric(TRUE)?

 
 
 
 

4. Assume the array books_array contains 6 elements. The array has three rows and two columns and appears as follows:

     [,1]              [,2]
[1,] "It"              "Dr. Sleep"
[2,] "Misery"          "Carrie"
[3,] "The Shining"     "The Mist"

Which of the following commands will return “The Shining”?

 
 
 
 

5. How many elements will be in vector $b$, if b <- 10:15

 
 
 
 

6. In R, which command should you use to insert a new row into a data frame?

 
 
 
 

7. In R, variables are typically assigned using <-, but they can also be assigned using which of the following symbols?

 
 
 
 

8. In R, which command will output the data from the Nile built-in data set?

 
 
 
 

9. In R language, which command returns the last six elements of a data object such as a data frame?

 
 
 
 

10. In R, assume you have a vector named “age,” and each element in the vector is the age of one person in a group. The vector has the following content: 24 32 46 19. What will be the result if you issue the age[-2] command?

 
 
 
 

11. In R, what is the result of the function as.integer(3.3)?

 
 
 
 

12. In R, assume you have a vector named “age,” and each element in the vector is the age of one person in a group. Which command must you use to reorder the ages from youngest to oldest?

 
 
 
 

13. All columns in a matrix must have the

 
 
 
 

14. Which command in R would return the following character vector? “Imdad” “Usman” “Ali” “Amir”

 
 
 
 

15. In R, which command removes a variable from memory?

 
 
 
 

16. To perform a one-way Analysis of variance, one can use a function

 
 
 
 

17. For a matrix $X$ of order $n\times p$ and a vector $Y$ of order $n\times 1$, one can find regression coefficients using

 
 
 
 

18. Assume that the function add is defined as follows:

add <- function(x,y) {
(x + y)
return (x - y)
temp <<- (x * y)
return (x / y)
}

What will be the output if you issue the command add(10,5)?

 
 
 
 

19. What is the first step you must take before you can read an Excel spreadsheet in R?

 
 
 
 

20. In R, assume a character vector called “names” has the following contents:

“Harry” “Jimmy” “Tammy”

Which command would return the following logical vector?

FALSE TRUE FALSE

 
 
 
 

Online R Programming Quiz with Answers

  • What is the main reason for using the R language?
  • In R, what is the result of the function as.numeric(TRUE)?
  • In R, variables are typically assigned using <-, but they can also be assigned using which of the following symbols?
  • Which command in R would return the following character vector? “Imdad” “Usman” “Ali” “Amir”
  • In R, assume you have a vector named “age,” and each element in the vector is the age of one person in a group. The vector has the following content: 24 32 46 19. What will be the result if you issue the age[-2] command?
  • Assume the array books_array contains 6 elements. The array has three rows and two columns and appears as follows:

    [,1]              [,2]
[1,] “It”              “Dr. Sleep”
[2,] “Misery”          “Carrie”
[3,] “The Shining”   “The Mist”

Which of the following commands will return “The Shining”?

  • In R language, which command returns the last six elements of a data object such as a data frame?
  • Assume that the function add is defined as follows:
    add <- function(x,y) {
    (x + y)
    return (x – y)
    temp <<- (x * y)
    return (x / y)
    }
    What will be the output if you issue the command add(10,5)?
  • What is the first step you must take before you can read an Excel spreadsheet in R?
  • After installing and calling the httr library in R, which method should you use to update a resource?
  • In R, what is the result of the function as.integer(3.3)?
  • In R, which command removes a variable from memory?
  • In R, assume a character vector called “names” has the following contents: “Harry” “Jimmy” “Tammy” Which command would return the following logical vector? FALSE TRUE FALSE
  • In R, assume you have a vector named “age,” and each element in the vector is the age of one person in a group. Which command must you use to reorder the ages from youngest to oldest?
  • In R, which command will output the data from the Nile built-in data set?
  • In R, which command should you use to insert a new row into a data frame?
  • To perform a one-way Analysis of variance, one can use a function
  • How many elements will be in vector $b$, if b <- 10:15
  • All columns in a matrix must have the
  • For a matrix $X$ of order $n\times p$ and a vector $Y$ of order $n\times 1$, one can find regression coefficients using
R Programming Quiz with Answrs

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Questions Data Types in R 2025

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This post is about Data Types in R language. It contains Interview Questions about Data Types. It contains some basic questions that are usually asked in job interviews and examinations vivas.

What are R data types?

In programming languages, a data type is a classification that specifies what type of a value variable can have. It also describes what type of relational, mathematical, and logical operations can be applied to it without causing an error. We need to use various variables to store information while coding in any programming language. Variables are nothing but reserved memory locations to store values. This means that when one creates a variable one reserves some space in memory. The variables are assigned with R-Objects. Thus, the data type of the R-object becomes the data type of the variable.

How Many Data Types in R Language?

There are 5 types of data types in R language, namely

  • Integer data type
  • Numeric data type
  • Character data type
  • Complex data type
  • Logical data type

What are the Data Types in R on Which Binary Operators Can Be Applied?

The binary operators can be applied to the data types (i) Scalars, (ii) Matrices, and (iii) Vectors.

What are the Types of Objects in R?

There are 6 types of objects in the R Language.

  • Vectors are the most important data type of object in R. A vector is a sequence of data elements having the same data type.
  • Matrices (and arrays) that are multi-dimensional generalizations of vectors. Matrices are arranged into a fixed number of rows and columns. The matrices (or arrays) are vectors that can be indexed by two or more indices and will be printed in special ways.
  • Factors provide compact ways to handle categorical data.
  • Lists are a general form of vector in which the various elements need not be of the same type and are often themselves vectors or lists. Lists provide a convenient way to return the results of a statistical computation.
  • Data frames are matrix-like (tabular data objects) structures, in which the columns can be of different types. Think of data frames as ‘data matrices’ with one row per observational unit but with (possibly) both numerical and categorical variables. Many experiments are best described by data frames.
  • Functions are themselves objects in R language which can be stored in the project’s workspace. Functions provide a simple and convenient way to extend R.

Note that vector, matrix, and array are of a homogenous type and the other two list and data frames are of heterogeneous type.

What is the difference between a Data Frame and a Matrix in R Language?

In R language data frame may contain heterogeneous data while a matrix cannot. Matrix in R stores only similar data types while data frame can be of different data types like characters, integers, or other data types.

What is the Factor Variable in R language?

In language, Factor variables are categorical (qualitative) variables that can have either string or numeric values. Factor variables are used in various types of graphics, particularly for statistical modeling where the correct number of degrees of freedom is assigned to them.

What is an Atomic Vector and How Many Types of Atomic Vectors are in R?

The atomic vector is the simplest data type in R. Atomic vectors are linear vectors of a single primitive type. There are four types of atomic vectors are present in R:

  • Numerical
  • Integer
  • Character
  • Logical
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