R Programming Interview Questions and Answers

R  programming language which can be used for several purposes including statistical analysis, data visualization, predictive modeling etc. Here we have compiled some R interview questions and answers that you should prepare for the interview. Going through these questions will help you to understand some of the important questions that can be asked in the interview.

What is R?

The development of statistical software and evaluation of data is the purpose of R. R comprises machine learning algorithms, time series, linear regression, statistical inference etc. Several of the R libraries are written in R. However for heavy computational task, one can take up C, C++ and Fortran codes.

How R Commands are Written?

R commands are written by using #  at the beginning of the line of code.

Name Some Functions Available in “dplyr” Package.

Functions in dplyr package:

  • filter
  • Select
  • arrange
  • mutate
  • count

What are the Advantages of R?

  • R is used for controlling and manipulating data.
  • R is an open source software
  • There are no restrictive license
  • There are excellent graphical capabilities.
  • R initiates on several Operating System and various hardware. It also initiates on 32 & 64 bit processors.

How Many Sorting Algorithms are Available?

  • Bubble Sort
  • Selection Sort
  • Quick Sort
  • Merge Sort
  • Bucket Sort

How to Create New Variable in R Programming?

Assignment operator ‘<-’ is used for creating new variable in R. 

For e.g. mydata$sum <- mydata$x1 + mydata$x2

What are R Packages?

Collection of data are called packages. These packages are saved in library.

 What is the Workspace in R?

Workspace is the present R working environment which comprises any user defined objects comprising vector, lists etc.

What is the Power Analysis?

Power analysis is applied for experimental design. It is helpful for making out the effect of given sample size.

Which Method is Used for Exporting the Data in R?

There are several ways to export the data into another format including SPSS, SAS, Excel Spreadsheet etc.

 What is the Use of Coin Package in R?

The Coin package offers an implementation of a general framework for conditional inference procedures generally called as permutation tests.

What is GGobi?

GGobi is an open source program which is used for visualization for getting insight into high dimensional typed data.

What is iPlots?

iPlots is a package that offers bar plots, box plots, mosaic plots, scatter plots, parallel plots, and histograms.

 Which Method is Used for Exporting the Data in R?

There are many ways to export the data into another formats like SPSS, SAS , Stata , Excel Spreadsheet.

Can you Write and Explain Some of the Most Common Syntax in R?

Few of the basic syntax for R that is used frequently are:

# —used to bring in a line of comments

“”-they indicate a string data type in R

<- —assignment operator (know this correctly as this is one of the strange things of R. It is not = for assignment operator.

\ — the backsplash denotes the escape character in R.

How do you Assign a Variable in R?

myVar <- 20

print(myVar

The following is also valid:

myVar = 15

print(myVar)

Assigning variables can also be performed the other way round. 

“helloWorld” -> myVar

The string “helloWorld” is now saved in the myVar variable. Note that this would generate an error if we got confused and attempted to plug an undefined variable object into a string, as in:

myVar -> “helloWorld”

Error: object ‘myVar’ not found

What are the Different Data Types/Objects in R?

At the time of assigning a variable, R does not ask users to declare a data type. On the other hand, everything in R correlated to an R data object. At the time of assigning a variable in R, you assign it a data object. That object’s data type makes up the data type of the variable. The frequently applied data objects are:

  • Vectors
  • Matrices
  • Arrays
  • Lists
  • Data frames
  • Factors

How do you Install a Package in R?

Several ways are available to install a package in R. The GUI Is also applied for some. 

Key in the following into your console and hit enter:

install.packages(“package_name”)

library(package_name)

While the first command installs the package the second command loads the package into the session.

What is a Factor Variable, and What is its Purpose?

A factor variable is a type of categorical variable. It accepts eight character or numeric string values. One of the major reasons to apply a factor variable is that it can be applied in statistical modeling with great correctness. Memory efficiency is another reason for applying them. You have to just use the factor() function for creating a factor variable. 

What are Different Ways to Call a Function in R?

A function in R can be called in 3 ways. 

  • First method- call by means of the position of the arguments.
  • Second method-call by means of the name of the arguments
  • Third method-call by means of default arguments.

Give the Syntax for Creating Scatterplot Matrices.

Pairs (Formula, Data)

Here formula represents the series of variables that are applied in pairs. Data represents the data set from which the variables will be considered. 

In R, How Missing Values are Represented ?

NA (Not Available) is the sign used for representing missing values in R.

Explain How Data is Aggregated in R?

This is done by collapsing data in R by applying one or more BY variables. While using the aggregate() function the BY variable should be available in the list. 

Hope these questions help you to understand what questions may be asked in an R interview. We have prepared them with care and we believe you go through them diligently for cracking the interviews with ease. 

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