Master Your Interview
Top 41 R Interview Questions
Entry Junior Mid Senior Expert
R Theoretical Questions
Q1:
What are the three important components of a function in R?
Entry
Q2:
How do you convert factors to numeric?
factors to numeric? Entry
Q3:
What is the use of next statement in R?
next statement in R? Junior
Q4:
Name some examples of when its appropriate to use the which() function
which() function Junior
Q5:
What's the difference between [ ] and [[ ]] for accessing the elements of a list or dataframe?
[ ] and [[ ]] for accessing the elements of a list or dataframe? Junior
Q6:
When to use the with() function and why is it good?
with() function and why is it good? Junior
Q7:
What are the Enclosing and Parent Environments and why are they important?
Junior
Q8:
How do you create a new column in a dataset based on some condition?
Junior
Q9:
What happens if you use the function switch() with numeric values?
switch() with numeric values? Junior
Q10:
How do you convert list or matrices to a data frame?
Mid Mid Mid Mid Q14:
How can you join dataframes using SQL style joins (inner, outer, left, right) in R?
join dataframes using SQL style joins (inner, outer, left, right) in R? Mid Q15:
What is the recycling of elements in a vector? Give an example.
Mid Q16:
Why is it not advisable to use attach() in R, and what should be used instead?
attach() in R, and what should be used instead? Mid Q17:
What are the sorting algorithms available in R?
Mid Q18:
What does the operator %>% do in R?
%>% do in R? Mid Q19:
How many types of vectors exist in R? What are the difference between them?
Mid Q20:
When would you use apply, lapply and sapply?
apply, lapply and sapply? Mid Q21:
How can you return multiple objects in an R function?
Mid Q22:
What are the differences between = and <- assignment operators in R?
= and <- assignment operators in R? Mid Q23:
Name some OOP systems available in R and when they could be useful
Senior Q24:
What's the correct way to specify optional arguments in R functions?
Senior Q25:
What is lazy function evaluation in R?
Senior Q26:
What is the difference between Factor Levels and Factor Labels and how does these work in the factor() function?
factor() function? Senior Q27:
How do you write summary methods?
Senior Q28:
Are there any problems with using the read.table() function?
read.table() function? Senior Q29:
Why does summary() report strange results for the R-squared estimate when we fit a linear model with no intercept?
summary() report strange results for the R-squared estimate when we fit a linear model with no intercept? Expert Q30:
How do you access the source code for a function in R?
Expert R Practical Challenges
Q1:
What does this code do? How do f2 and f3 differ from f1?
f2 and f3 differ from f1?
Junior Q2:
How can you count vowels in a string?
Junior Q3:
Why do the two expressions below not return the same result?
Junior Q4:
How can you count the number of times a value x appears in a vector?
x appears in a vector? Junior Q5:
What happens if you attempt to set row names that are not unique?
Mid Q6:
Why is 1 == "1" true? Why is -1 < FALSE true? Why is "one" < 2 false?
1 == "1" true? Why is -1 < FALSE true? Why is "one" < 2 false? Mid Q7:
What does the following function in R return?
Mid Q8:
What type of vector does each of the following calls to ifelse() return?
ifelse() return? Mid Q9:
How to pull out p-values and R-squared values from a linear regression model?
Mid Q10:
What does this function in R return? Explain
Senior Q11:
Why are the numbers provided in the code below are not equal?
Senior 
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