Name:
Andrew ID:
Collaborated with:
This lab is to be completed in class. You can collaborate with your classmates, but you must identify their names above, and you must submit your own lab as an Rmd file on Blackboard, by 11:59pm on the day of the lab.
There are Homework 1 questions dispersed throughout. These must be written up in a separate Rmd document, together with all Homework 1 questions from other labs. Your homework writeup must start as this one: by listing your name, Andrew ID, and who you collaborated with. You must submit your own homework as a knit HTML file on Blackboard, by 6pm on Sunday September 11. This document contains 14 of the 45 total points for Homework 1.
Important remark on compiling the homework: many homework questions depend on variables that are defined in the surrounding lab. It is easiest just to copy and paste the contents of all these labs into one big Rmd file, with your lab solutions and homework solutions filled in, knit it, and submit the HTML file. So for Homework 1, e.g., you should paste your solutions (including solutions to homework questions) from Lab 1w, Lab 1f, Lab 2w, and Lab 2f into one big Rmd file, knit it, and submit it.
bill = "Bill Clinton"
others = c("George Bush", "Ronald Reagan", "Jimmy Carter", "Gerald Ford")Display the first 5 letters from the string bill.
Display the first 5 letters from each of the strings in the vector others.
Join bill and others together into one vector of strings, called presidents.
Display the last 3 letters from each of the strings in the vector presidents.
Copy presidents over to a new string presidents.borg. Replace the last 4 letters in each of the strings in presidents.borg with “borg”. Display the results.
Hw1 Q1 (2 points). Replace the last letter in each of the strings in presidents with the last letter of one of the other strings, randomly swapped. Display the results.
Hw1 Q2 (5 points). Explain the following replacement results.
college = "Dietrich"
substr(college, 5, 9) = "right"
college## [1] "Dietrigh"college = "Dietrich"
substr(college, 1, 3) = "Live"
college## [1] "Livtrich"words = c("fat", "hat", "lamp", "glade")
substr(words, 1, 1) = c("c", "b")
words## [1] "cat" "bat" "camp" "blade"animals = c("cat", "lion", "piggy", "chicken")
substr(animals, 1, 5) = c("kitty", "doggy")
animals## [1] "kit" "dogg" "kitty" "doggyen"subjects = c("Statistics", "Computer Science", "Mathematics", "Engineering")
ratings = c("Good", "Bad")
substr(subjects, nchar(subjects)-nchar(ratings)+1, nchar(subjects)) = ratings
subjects## [1] "StatisGood" "Computer ScieBad" "MathemaGood"
## [4] "EngineerBad"presidents = c("Bill Clinton", "George Bush", "Ronald Reagan", "Jimmy Carter", "Gerald Ford")Split each string in the vector presidents into two strings, according to first and last name. Save the resulting list as presidents.list, and display it (the result should be a list).
Display names of only the democrats in presidents.list.
Hw1 Q3 (2 points). Run the command presidents.mat = matrix(unlist(presidents.list), 5, 2, byrow=TRUE), and display and explain the result. What would have happened without the byrow=TRUE?
strsplit(presidents[4], split="o")## [[1]]
## [1] "Jimmy Carter"strsplit(presidents, split=c(" ", "o"))## [[1]]
## [1] "Bill" "Clinton"
##
## [[2]]
## [1] "Ge" "rge Bush"
##
## [[3]]
## [1] "Ronald" "Reagan"
##
## [[4]]
## [1] "Jimmy Carter"
##
## [[5]]
## [1] "Gerald" "Ford"Create a vector of strings vice.presidents, containing the vice presidents corresponding to the presidents in presidents (look them up on the web if you need to…). Create another vector of strings pairs, by joining together each president with his vice president, separated by " & “. So, the first string in pairs should be”Bill Clinton & Al Gore“. Display the results.
Collapse the vector pairs in the previous question into a single string, where each pair of president and vice president is separated by “,”, so the string should read “Bill Clinton & Al Gore, George Bush & …”.
Do the same as in the previous question, but with the president and vice presidents listed in chronological order, i.e., starting with Ford and his vice president, and finishing with Clinton and Gore. (Hint: use rev().)
Hw1 Q4 (3 points). Create a 5 x 2 matrix vice.presidents.mat, with the first column containing first names of vice presidents, and the second column containing last names. (Hint: follow Hw1 Q3 and the code leading up to this.) Now use presidents.mat and vice.presidents.mat to build a string that contains the last name of each president and his vice president pair, with the names separated by “+” and the pairs by “,”. So, the final string should be of the form “Clinton+Gore, Bush+…”. (Hint: this last step can be done with a single paste() call.)
Hw1 Q5 (2 points). Do the same as in the previous question, but with each president assigned a random vice president. So, the final string should be of the form “Clinton+Quayle, Bush+…”, where Clinton’s vice president was chosen randomly from the 5 possibilities in vice.presidents. (Hint: scramble the second column of vice.presidents.mat before proceeding with the usual workflow.)