R Practice Exercises: Level 1 (Beginners)

Q1. Using R as a calculator

Exercise 1: Calculate square root of 729 SelectShow


Q2. Creating a numeric variable

Exercise 2: Create a new variable 'b' with value 1947.0 SelectShow


Q3. How to convert a numeric variable to character

Exercise 3: Convert 'b' from previous exercise to character SelectShow


Q4. Setting up working directory

Exercise 4: Setup your working directory to a new 'work' folder in your desktop SelectShow


Q5. Create an environment within the global environment

Exercise 5.1: Create a new environment called 'myEnv' SelectShow

Exercise 5.2: Create a variable inside it SelectShow

Exercise 5.3: Access the variable inside the new environment SelectShow

Exercise 5.4: Delete the variable inside that environment SelectShow


Q6. Create a numeric vector

Exercise 6.a: Create a vector numbers from 1 to 6 and find out its class SelectShow

Exercise 6.b: Create a vector containing following mixed elements {1, 'a', 2, 'b'} and find out its class SelectShow


Q7. Initialise Character vector

Exercise 7.a: Initialise a character vector of length 26 SelectShow

Exercise 7.b: Assign the character 'a' to the first element in above vector. SelectShow


Q8. Vector operations

Exercise 8.1: Create a vector with some of your friend's names SelectShow

Exercise 8.2: Get the length of above vector SelectShow

Exercise 8.3: Get the first two friends from above vector SelectShow

Exercise 8.4: Get the 2nd and 3rd friends SelectShow

Exercise 8.5: Sort your friends by names using 2 methods SelectShow

Exercise 8.6: Reverse direction of the above sort SelectShow


Q9. Create customised vector sequences

Exercise 9: Create with rep and seq: 'a','a',1,2,3,4,5,7,9,11 SelectShow


Q10. Remove missing values

Exercise 10: Remove missing value from c(1, 2, NA, 4) SelectShow


Q11. Random sampling

Exercise 11: Pick 50 random numbers between 1 to 100, with replacement SelectShow


Q12. Checking the class

Exercise 12: Check the class of mySample SelectShow


Q13. Find the class of ‘iris’ dataframe, find the class of all the columns of ‘iris’, get the summary of ‘iris’, get the top 6 rows, view it in a spreadsheet format, get row names, get column names, get number of rows and get number of columns.

Exercise 13: Apply the above functions and inspect results on 'iris' (a base R dataframe) SelectShow


Q14. Subsetting a dataframe

Exercise 14.1: Get the last 2 rows in last 2 columns from iris dataset SelectShow

Exercise 14.2: Get rows with Sepal.Width > 3.5 using which() from iris SelectShow

Exercise 14.3: Get the rows with 'versicolor' species using subset() from iris SelectShow


Q15. With the dataframes created from code below, perform the various merge operations.
Df1 <- iris[sample(1:nrow(iris), 10), c(1,2,3,5)]
Df2 <- iris[sample(1:nrow(iris), 10), c(1,2,4,5) ]
# induce NAs
Df1 <- Df1[sample(1:nrow(Df1), 3), 4]
Df2 <- Df2[sample(1:nrow(Df1), 3), 4]

Exercise 15.1: Find out how to do inner join, outer join, left join and right join. Merge using the by variable as 'Species' SelectShow

Exercise 15.2: How would you specify the 'by' variables if the two data frames to be merged have different 'by' variables. SelectShow


Q16. Create customised character vector using the paste function

Exercise 16: Create this character vector using paste: 'var1', 'var2', 'var3', 'pred1', 'pred2', 'pred3' SelectShow


Q17. Creating tables

Exercise 17: Tabulate the Sepal.Width for each Species from iris SelectShow


Problem Logic for Q18, 19 and 20: Create a character vector with length of number-of-rows-of-iris-dataset, such that, each element gets a character value – “greater than 5″ if the corresponding ‘Sepal.Length’ > 5, else it should get “lesser than 5″.

Q18. Create a logic for the above problem using a For-loop

Exercise 18: Make the logic for above problem statement using a 'for-loop' and a 'if-else' statement SelectShow

Q19. ifelse() function
Exercise 19: Make the logic for above problem statement using a ifelse() function SelectShow


Q20. The apply() function

Exercise 20: Create a logic for the same problem statement using apply() function SelectShow


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