R Programming FAQs - R Tutorials, Tips, Solutions for Data Analysis & Visualization

R and Database Management System Quiz 20

February 1, 2025February 1, 2025 by Muhammad Imdad Ullah

The post is about R and Database Management System Quiz with Answers. There are 20 multiple-choice questions about R language and database connectivity with R. Let us start with the R and Database Management System Quiz now.

R and Database Management System Quiz

How can a relational database help R handle memory issues?
Which R function saves a single data structure to a .Rda file?
Which of the following concepts illustrates a data frame in R language?
When mapping data types between R and a database, which of the following should you consider converting to strings?
When designing a relational database, which aspect is primarily addressed by normalization techniques?
Which of the following is the simplest way to update individual observations in a data frame?
A variable in R language is comparable to which of the following relational database concepts?
In the context of mapping data between R and relational databases, how does logical data from R typically represent when exchanged with a database server?
What benefit does using a relational database with R provides even when the data does not reside in the database?
Choose a statement that best describes declarative referential integrity.
Which function in the RJDBC package is used to close the database connection after accessing the data?
What does RJDBC stand for?
Which of the following statements about database packages for R are true?
Which of the following statements correctly describes the ODBC Driver Manager?
What are the two categories of relational database access packages in R language? https://rfaqs.com
Which of the following is the first step that you must take before using the RJDBC package for R language? https:/rfaqs.com
Which of the following is one of the two components of ODBC?
What is the best way to provide a data analyst with knowledge of a database schema or structure, often depicted using an entity-relationship (ER) diagram?
Which RODBC function is best suited for retrieving information about the structure and attributes of database tables?
What is the first step you must complete outside of R before installing the RODBC package?

Sociology Quiz with Answers

Statistical Simulation

Matrices in R Programming

March 14, 2025January 28, 2025 by Muhammad Imdad Ullah

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)
                   )

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.

Rfaqs.com matrices in R Programming Language

Statistics and Data Analysis

R Programming Quiz 19

January 20, 2025January 20, 2025 by Muhammad Imdad Ullah

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.

Please go to R Programming Quiz 19 to view the test

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