date()
## [1] "Thu Sep 13 00:36:00 2012"
Due Date: September 13, 2012
Total Points: 30
1 The following values are the annual number hurricanes that have hit the United States since 1990. Follow instructions and answer questions by typing the appropriate R commands.
0 1 1 1 0 2 2 1 3 3 0 0 1 2 6 6 0 1 3 0 1
a. Enter the data into R. (2)
counts = c(0, 1, 1, 1, 0, 2, 2, 1, 3, 3, 0, 0, 1, 2, 6, 6, 0, 1,
3, 0, 1) # annual number hurricanes that have hit the United States since 1990
b. How many years are there? (2)
length(counts) # length of data vector
## [1] 21
c. What is the total number of hurricanes over all years? (2)
sum(counts) # total number of hurricanes making landfall
## [1] 34
2 Answer the following questions by typing the appropriate R commands.
a. Create a vector of numbers starting with 0 and ending with 25. (2)
counts.d2 = c(0:25) # integers 0 through 25
b. What is the length of this vector? (2)
length(counts.d2) # number of integers in counts.d2
## [1] 26
c. Create a new vector from the original vector by subtracting the mean
value over all numbers in the vector. (2)
x = counts.d2
xbar = mean(x)
x - xbar
## [1] -12.5 -11.5 -10.5 -9.5 -8.5 -7.5 -6.5 -5.5 -4.5 -3.5 -2.5
## [12] -1.5 -0.5 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5
## [23] 9.5 10.5 11.5 12.5
3 Suppose you keep track of your mileage each time you fill up. At your last 8 fill-ups the mileage was
65311 65624 65908 66219 66499 66821 67145 67447
a. Enter these numbers into a vector called miles. (2)
miles = c(65311, 65624, 65908, 66499, 66821, 67145, 67447) # mileage at each of last 8 fill-ups
b. Use the function diff() to determine the number of miles between fill-ups. (2)
diff(miles) # amount of miles in between each fill-up
## [1] 313 284 591 322 324 302
dm = diff(miles)
c. What is the maximum, minimum, and mean number of miles between fill-ups? (3)
max(dm) # most miles in between fill-ups
## [1] 591
min(dm) # least miles in between fill-ups
## [1] 284
mean(dm) # average miles traveled in between fill-ups
## [1] 356
4 Create the following sequences using the seq() and rep() functions as appropriate.
a. “a”, “a”, “a”, “a” (2)
rep("a", times = 4)
## [1] "a" "a" "a" "a"
b. The odd numbers in the interval from 1 to 100 (2)
seq(from = 1, to = 100, by = 2)
## [1] 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45
## [24] 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91
## [47] 93 95 97 99
c. 1, 1, 1, 2, 2, 2, 3, 3, 3 (2)
rep(c(1, 2, 3), c(3, 3, 3))
## [1] 1 1 1 2 2 2 3 3 3
d. 1, 1, 1, 2, 2, 3 (2)
rep(c(1, 2, 3), c(3, 2, 1))
## [1] 1 1 1 2 2 3
e. 1, 2, 3, 4, 5, 4, 3, 2, 1 (3) Hint: Use the c() function.
t = c(1, 2, 3, 4, 5, 4, 3, 2, 1)
t
## [1] 1 2 3 4 5 4 3 2 1