Interview Questions.

Top R Interview Questions and Answers in 2021


Top R Interview Questions and Answers in 2021

R programming language is used for statistical evaluation, graphical illustration, and reporting. R is freely to be had below the GNU General Public License (GNU GPL) GNU GPL lets in quit-consumer to use the software program with the liberty to run, proportion and use the software. R programming language is used inside the subject of regression analysis, predictive modeling, possibility estimation, data mining which further enables in records evaluation. This article will will let you prepare for the imminent R interview with the below indexed pleasant R Interview Questions and Answers.

Top R Interview Questions and Answers

Features of R programming language:

R is used to address a large quantity of statistics and garage facilities.

R is handy whilst handling statistical evaluation and graphical representation of records.

R presents a big wide variety of operators to perform the calculation on arrays, lists, vectors, and metrics.

Here is a list of R interview questions to help you put together for that interview and get a process in the discipline of statistics science.

Question: What is the facts shape in R, which facilitates in statistical evaluation and graphical representation?

Answer: The following are the statistics structure in R, that is extensively used:




Data Frame



Question: How to print some thing in R? <Practice of R basic syntax>

Answer: To write some thing, R makes use of print command.

>string_variable_name <- “R is an analytical language”

Question: What is class() function R?

Answer: This feature in R is a character vector giving the names of classes shape which the item inherits.


>x <- 1:10
[1] “integer”

Question: What is a vector?

Answer: A vector is a sequence of information elements of the equal number one kind. Members in a vector are known as additives.


>vector_example <- c(2,3,4,5)
> print(vector_example)
[1] 2,3,4,5
>print (length(vector_example)
[1] 4

Question: How to perform mathematics operations on Vectors? Show with a few instance

Answer: Many mathematics operators are used in R. Remember, R makes use of the operators issue by way of element. Let’s examine it with a few standard operators.

>x <- c(1,2,3,4)
> y <- c(4,5,6,7)
> x+y
[1] 5 7 9 11
> x-y
[1] -3 -3 -3 -3
> z <- (4,4,4,4,4,4,4)
> x+z
[1] 5 6 7 8 5 6 7

When we have two vectors with unequal lengths, and we want to operate on both, then the shorter vector is used again and again to match the period of both the vectors.

Question: Define Index in Vector.

Answer: Index inside the vector is used to give the element at that function of the vector. Few programming languages start the index with zero, and the alternative begins at 1. R counts the index from 1. There are many possibilities at the same time as setting an index range i.E.

1. Positive and in variety index

> x<- (1,3,4,5)
> x[2]
[1] “3”

2. Out of range

>x <- (2,3,4,5)
> x[110]
[1] NA

three. Negative index- eliminates this element and replies again with all the left numbers.

> x <- (3,4,5,6,7)
> x[-3]
[1] “3” “4” “6” “7”

four. Range of values

>x <- (3,4,5,6,7,8)
> x[2:5]
[1] “4” “5” “6” “7”

5. Duplicate index

>x <- (3,4,5,6,7)
[1] “4” “3” “4” “5”

6. Logical index

If we want to pick a specific group of an index number, then you definitely need to use logical operators i.E., TRUE and FALSE

> x <- (2,3,4,5,6)
[1] “2” “5” “6”

Question: What is a listing?

Answer: A listing, as the name indicates, are numerous vectors accumulated together. Suppose you have got a numeric vector, a individual vector, a Boolean vector, and some numbers. We want to mix it into one, which glaringly gained’t have the identical statistics type. So we need to create a list.

> n = c(2,3,5)
> s = c (“a”, “b”, “c”, “d”, “e”)
> x = list (n, s, b, 3)
> print(x)
[1] 2 3 5
[1] “a” “b” “c” “d” “e”
[1] 3

Question: What is Matrices?

Answer: A matrix is a -dimensional square data set. It may be created using a vector input to the matrix feature.


# Matrix creation
> M = matrix(c(1,2,3,4,5,6), nrow=2, ncol=3, by-row =TRUE)
[1] [2] [3]
[1] 1 2 3
[1] 4 5 6
nrow = number of rows in the matrix
ncol = number of columns in the matrix
byrow = TRUE/FALSE will get value first by row or column.

Question: What is an Array?

Answer: Array is a superset of Matrices. On the only hand, the matrices may be of 2 dimensions, however the array can be of any variety of dimensions.


> a<- array(c(“car”, “bike”), dim (3,3,2))
> print (a)
, , 1
[,1] [,2] [,3]
[1,] “car” “bike” “car”
[2,] “bike” “car” “bike”
[3,] “car” “bike” “car”
, , 2
[,1] [,2] [,3]
[1,] “bike” “car” “bike”
[2,] “car” “bike” “car”
[3,] “bike” “car” “bike”
>my_array <- array(1:24, dim = c(3,4,2))
< my_array
, , 1
[,1] [,2] [,3] [,4]
[1,] 1 4 7 10
[2,] 2 5 8 11
[3,] 3 6 9 12
, , 2
[,1] [,2] [,3] [,4]
[1,] 13 16 19 22
[2,] 14 17 20 23
[3,] 15 18 21 24

Question: What is the factor?

Answer: Factors are the r-objects which are created using a vector. Factors in R are stored as a vector of integer values with a corresponding set of character values to use when the factor is displayed. The factor function is used to create a factor. The only required argument to factor is a vector value which will be returned as a vector of factor values. It stores the vector along with the distinct values of the elements in the vector labels.

Factors are created using the factor() function. The nlevels functions give the count of levels.


#First let’s create a vector
>vector_example <- c(‘a’, ‘b’, ‘c’, ‘a’, ‘a’)
#Now create a factor object
>factor_example <- factor(vector_example)
[1] a b c a a
[1] 3

nlevels offers you the number of awesome values within the vector.

Question: What is the distinction among Matrix and an array?

Answer: Matrix may have most effective  dimensions, while an array can have as many dimensions as you want. Matrix is defined with the help of records, variety of rows, wide variety of columns, and whether the elements are to be put in row-wise or column-clever.

In array, you want to provide the dimension of the array. An array can be of any range of dimensions, and each size is a matrix. For instance, a 3x3x2 array represents two matrices, each of size 3x3.

Question: What is a data body?

Answer: The statistics frame is a listing of vectors of equal duration. It can include any vector with a particular kind and might combine it into one. So, a information body can have a vector of logical and every other of numeric. The simplest circumstance is that each one the vectors ought to have the identical period.


#This is how the data frame is created
> student_profile <- data.frame(
Name <-c(“Ray”, “Green”, “Justin”)
Age <- c(22,23,24)
Class <- c(6,7,8)

The above code will create 3 columns with the columns name as name, age, and class.

Question: What is the distinction among a matrix and a data frame?

Answer: A data frame can include vectors with special inputs, and a matrix cannot. We could have a records frame of characters, integers, and even other statistics frames, however you may’t do this with a matrix considering that a matrix must be all the same kind.

So, the statistics frame will have a special vector of man or woman, numbers, and common sense.

But, for the matrix, we want best one sort of statistics type.

Question: How to read enter from the person in R?


Readinteger <- characteristic()

Readinteger <- function()
n <- readline(prompt = “Enter an integer: “)

Readline lets the user input one line string in R.

The spark off argument is printed on the display of the consumer.

Question: Write a feature to get the rectangular of various


Square <- function(x) {

Question: How to apply mode characteristic in R?

Answer: The mode is the value that has the very best variety of occurrences in a fixed of facts. Unlike the imply and median, the mode will have both numeric and person statistics.

R does now not have a general in-constructed function to calculate the mode. So we create a person function to calculate the mode of a data set in R. This characteristic makes the vector as enter and gives the mode value as output.


imer <- function(time)
Time <- time -1
[1] 5
[2] 4
[3] 3
[2] 2
[1] 1

Question: What does an enlist feature does?

Answer: It converts a list to a vector

Question: What is the follow feature in R?

Answer: follow(), and its family is one of the most used functions in R. We use observe whilst we need to apply a function to the rows or columns of the matrix.


M<- matrix(seq(1,16),4,4)
apply (M,1,min)
[1] 1 2 3 4

Question: What is the lapply() characteristic in R?

Answer: lapply() feature is used whilst we need to apply a function to each

Question: Differentiate among lapply and sapply

Answer: If the programmers need the output to be a records body or a vector, then the sapply characteristic is used, while if a programmer wants the output to be a list, then lapply is used.

Question: How to put in a brand new package deal in R?

Answer: We need to recognise the call of the package deal



Question: What is the feature of merge() characteristic?

Answer: We can merge  information frames through the use of the merge feature(). The facts frames need to have the equal column names on which merging takes place.


df1 <- data.frame(id <- c(1:6), name <-c(rep(“Amit”,3), rep(“Sumit”,3))
df2 < - data.frame(id <- c(7,8,9), name <- c(rep(“Nitin”,2),rep(“Paplu”,1))
*outer join
merge(x=df1, y= df2, by =”id”, all TRUE)

This all = TRUE will give you the outer be part of, so the brand new information set may have all the price from both the statistics frames merged at the id.

Question: What is information cleaning?

Answer: Data cleansing is a technique in analytics that includes disposing of or amending data in a database that is inaccurate, incomplete, improperly formatted, or duplicated.

Question: What is information reshaping?

Answer: Sometimes, we want data in a particular format. Initially, we import the facts from a particular .Csv file or txt document in a information frame. But, most of the time we also need a records set this is unique from the initial data set plus we additionally need to add columns or role of the columns. So all this is records reshaping wherein you provide the shape of the initial facts frame in step with the want.

Question: Write a function to add two numbers in R


add <- function(a,b)
c <- a+b

Question: How can R be closed from the command line?

Answer: Use the feature q()

Question: How to examine the csv_input document in R?


data <- read.csv(“csv_input.csv”)

Question: Explain the use of the scan function in R.

Answer: The scan() function is used to read various types of data or data objects, for example, data vectors. The command can be customized to read specific data. The command waits for input from the data and then return the value entered at the prompt.

Question: What are the different file formats using in the R programming language?


.RDA file format: These are the R objects that are used to attaching and loading files in R.

.Rfiles: These are the files that are created inside the R editor by the dump function.

.Txt files: The .Txt files are used to store datasets. R uses theread.Table() and write.Table() function.

.Csv files: The comma-separated values files are common data files.

Question: What is the function od summary() function?

Answer: summary() is an important command which helps us to get the statistical summary of the data. It contains all the statistical data like mean, median, min, max, 1st quartile, and 3rd quartile.

Question: How can you add datasets in R?

Answer: rbind() function can be used to add datasets in R language provided the columns in the datasets should be the same.

Question: What are the factor variables in the R language?

Answer: Factor variables are categorical variables that hold either string or numeric values. Factor variables are used in various types of graphics and particularly for statistical modeling, where the correct number of degrees of freedom is assigned to them.

Question: What is the use of the seq() function in R?

Answer: seq() function in R is used to provide the user with a sequence of numbers. If we need a sequence of numbers with a particular step i.E., 4,8,12,16, then we need to provide another attribute “by = ?” which will provide the steps.


> print(seq(5,11, by = 2))

[1] 5,7,9,11

Question: Define repeat loop

Answer: Repeat loop executes a series of statements multiple times. It doesn’t positioned the situation at the equal vicinity wherein we placed the keyword repeat.


>name <-c(“Parry”,”John”)
>temp <-5
> repeat {
temp <- temp +2
if(temp >11){

This could go back the name vector four instances. First, it prints the name and will increase the temperature to 7 and so on.

Question: How can one perform selection making in R?

Answer: Decision making in R is completed inside the identical manner as in other languages. The three most important selection-making statements include:

If declaration

If.Else announcement

Switch statement

Question: There exist two vectors, a <- (3,four,five) and b <- (1,2), then what's going to be the output for c <- a * b?

Answer: c<- (three,8,five)

Question: What are the binary features in R on which binary operators can be applied?

Answer: Scalars, Matrices, and Vectors

Question: What are the main traits of a facts body?

Answer: The following are the main characteristics:

Row names need to be unique.

The column name need to be non-empty

There are simplest 3 types supported via the facts saved within the statistics body i.E., variety, element, and person.

Each column have to have the same number of statistics gadgets. This is one of the important policies of information frames.

Question: Explain the use of string function in R

Answer: The str() characteristic in R is used to get the shape of a statistics body at the side of the primary few observations. Suppose a information body has 4 variables, each with three values. Then the output of this feature can be like:

‘data.frame’: 3 obs. And 4 variable
$name: chr “Nitin” “Kamal” “Xtramous”
$age : int 16 18 20
$class: int 6 8 10

Question: What is the distinction between seq(4) and seq_along(four)

Answer: seq(4) produces a vector from 1 to four (c(1,2,three,four)), whereas seq_along(four) produces a vector of period(4), or 1(c(1)).

Question: How to read a .Csv file in R?

Answer: read.Csv() function is used to examine a CSV (Comma Separated Values) from the modern-day operating listing.


data_store<- read.csv(“abc.csv”)

Question: Get all of the statistics of the person having a maximum profits.


max_salary_person <- subset(data,
salary == max(salary))

Question: How to get outer be part of, left join, proper be a part of, internal be a part of, and pass join?

outer join - merge (x= df1, y=df2, by= “id”, all= TRUE)
left join - merge (x= df1, y= df2, by = “id”, all.x = TRUE)
right join - merge (x= df1, y= df2, by = “id”, all.y = TRUE)
inner join - merge (x= df1, y= df2, by = “id”)
cross join - merge (x= df1, y= df2, by = NULL)

Question: What do you imply with the aid of casting? What is the usage of forged() characteristic?

Answer: It is used to get combination after melt(). So, now we've got statistics arranged in a few order, if we want to aggregate the columns with similar company_name and age, then we ought to use the cast() function.


Casted_data_set <- cast(new_data_set, company_name+age ~ variable, sum)

The characteristic gives the mixture revenue and range of kids with the equal enterprise and age.

Question: What is the usage of sample characteristic in R programming?

Answer: Sample() function can be used to pick out a random sample of size ‘n’ from a large dataset.

Question: What is the usage of subset characteristic in R programming?

Answer: Subset() feature is used to pick variables and observations from a given dataset.

Question: What is the characteristic of the rnorm() characteristic? Explain with syntax.

Answer: rnorm characteristic generates “n” normal random numbers primarily based at the mean and preferred deviation arguments handed to the feature.


rnorm(n, mean = , sd= )

Question: How to make a scatterplot in R?

Answer: Scatterplot is a graph which suggests many factors plotted within the Cartesian aircraft. Each factor holds  values which can be gift at the x and y-axis. The simple scatterplot is plotted using plot() function.

The syntax for scatterplot is:



x is the information set whose values are the horizontal coordinates

y is the records set whose values are the vertical coordinates

major is the tile in the graph

xlab and ylab is the label in the horizontal and vertical axis

xlim and ylim are the bounds of values of x and y used within the plotting

axes imply whether each axes must be there on the plot.

plot(x = input$wt,y = input$mpg,
xlab = “Weight”,
ylab = “Mileage”,
xlim = c(2.5,5)
ylim = c(15,30)
main = “Weight vs Mileage”

Question: What is the sink function in R?

Answer: The sink() function defines the route of the output.

#direct output to a file
sink(“myfile”, append = FALSE, split = FALSE)
#return output to the terminal sink()

The append option controls whether or not output overwrites or provides to a document. The cut up choice determines if the output is likewise despatched to the screen as the output report.


We have supplied you with the famous R programming interview questions to your preparations for the records science interview. These R Interview Questions are the best set of interview questions. We also advocate that you exercise coding before you seem for an interview, and having a dummy challenge that you have worked on is always a plus. Do you have another questions which you have encounter for your interview? Or any other suggestions that you would really like to percentage with the R network?