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Summer R Bootcamp

Problem Set 1

 

Problem 1

 

  1. Create vectors containing {3.1, 4.1, 5.1, 6.1, 7.1, 8.1} elements in three different ways using the following functions: c(), seq() with a by argument, and seq() with a length.out argument. Name them vector1, vector2, and vector3, respectively.

 

  1. Add three new elements to vector1: 10, 20, 30. 10 should be the first element in the vector, 20 should be the 3rd element in the vector given that 10 has been already added to it, and 30 should be the 6th element in the vector given that 10 and 20 have been already added to the vector.

 

  1. Create a new vector containing {2, 3, 6, 10, 15, 18, 22, 25, 27, 30, 31, 35, 42} elements. Name it vector4. Extract/Select elements that are greater than 5 and are divisible by 3 using a logical statement and create a new vector vector5 with these elements. Check whether element 27 is in vector5 using a logical operator.

 

Problem 2

 

  1. Create a list with the following elements: [1, 50, 88], [“yesterday”, “today”, “tomorrow”], 22.5, [33.8, 42], “class_0001”. Name it list1.

 

  1. Apply unlist() function to list1. What are the data type and data structure of the output? What do you think why you got this specific data type?

 

  1. Create a new list (name it list2) by removing the third element of the first element of list1. Then extract/select the second and third elements of the second element of list2.

 

  1. Create a new list with the following elements: 23, “new”, 45.7. Name it list3. Now create a new list (name it list4) by merging list2 and list3 with a c(). How many elements does list4 contain (use a built-in function to count). Extract the first element of list4 as a list and as a vector.

 

Problem 3

 

  1. Create a data frame (name it df1) with the following variables:

    • Name - {“James”, “Linda”, “Stacy”, “Mary”, “Tom”, “Anna”, “Bob”, “Jeniffer”, “Lucas”, “Amy”, “Jim”}
    • Major - {“Math”, “Math”, “Genetics”, “Statistics”, “Accounting”, “Art”, “Music”, “Business”, “Finance”, “Finance”, “Math”}
    • Grad_Year - {2023, 2025, 2025, 2024, 2026, 2024, 2025, 2025, 2023, 2026, 2024}
    • GPA - {3.9, 3.75, 4.0, 4.0, 3.4, 3.9, 3.3, 3.8, 3.55, 4.0, 3.6}

 

  1. After you created df1, capitalize its column names. Get a 6-number summary of GPA column. What is a data type of GRAD_YEAR column? What should it be? Convert it into the correct data type. Display the frequency of its elements.

 

  1. Use a simple ifelse statement to add a new column NEXT_YEAR to the df1. This would be a boolean column, indicating TRUE if a student is graduating next year (2024) and FALSE if not (Check GRAD_YEAR column to see what year a student plans to graduate).

 

  1. Extract/Select all students in the df1 who is majoring in Math and is not going to graduate this year (2023).

 

Problem 4

 

  1. Create a matrix with 5 columns filled by columns with the following elements: 10, 3, 6, 23, -5, -4, 13, 17, 5, 6, -7, -10, 13, 39, 20, 2, 1, 9, 11, -22, 23, -15, -3, 6, 12. Name it matrix1.

 

  1. Use a For loop to replace elements of matrix1 as follows: if an element has a negative value, replace it with 0, if an element is greater than or equal to 10, replace it with 10, and if an element is greater than or equal to 0 and less than 10, replace it with 5.

 

  1. Create an empty vector vector6. Use a While loop to populate vector6 as follows: populate vector6 with odd numbers that are greater than 0 and less than 30 skipping odd numbers that are divisible by 3.

 

Problem 5

 

  1. Create a function (name it fun1) that will take a numeric vector as input and will extract elements of the input vector that are greater than 10. Do it in two ways: using for loop combined with conditional statement, and without it (using logical and extraction operators). Test your function with the following vector: [1, 4, 45, 23, 7, 9, 12, 15, 33]

 

  1. Create a function (name it fun2) that will take two matrices as inputs (mat1 and mat2) and will produce another matrix that has its elements populated as follows: if an element in mat1 is greater than the corresponding element in mat2, then the corresponding element in the output matrix would be "Greater than"; if an element in mat1 is less than the corresponding element in mat2, then the corresponding element in the output matrix would be "Less than"; and if an element in mat1 is equal to the corresponding element in mat2, then the corresponding element in the output matrix would be "Equal to".

    For example, if mat1[1, 1] = 10 and mat2[1, 1] = 5, then the output matrix will have "Greater than" element at [1, 1] position. Test your function with the following matrices: [1, 4, 9, 5, 2, 7, 4, 3, 10], 3 rows and filled by row; [2, 3, 10, 9, 1, 4, 4, 3, 9], 3 rows and filled by row.