Homework 3 - Vectors

In the code chunk below:

1. Create a vector even that holds the even numbers from 1 to 100
2. Using the all() function and %% (modulo) operator, confirm that all of the numbers in your even vector are even

even <- seq(2, 100, by=2)
even

##  [1]   2   4   6   8  10  12  14  16  18  20  22  24  26  28  30  32  34  36  38
## [20]  40  42  44  46  48  50  52  54  56  58  60  62  64  66  68  70  72  74  76
## [39]  78  80  82  84  86  88  90  92  94  96  98 100

all_are_even <- all(even %% 2 ==0)
print(all_are_even)

## [1] TRUE

In the code chunk below:

3. Create a vector phone_numbers that contains the numbers 2, 8, 1, 3, 3, 0, 8, 0, 0, 4
4. Create a vector prefix that has the first three elements of phone_numbers
5. Create a vector small that has the values of phone_numbers that are less than or equal to 5
6. Create a vector large that has the values of phone_numbers that are strictly greater than 5
7. Replace the values in phone_numbers that are larger than 5 with the number 5
8. Replace every odd-numbered value in phone_numbers with the number 0

For question 4, please don’t just do 2,8,1, use indexing! For questions 5 through 8, you should use not use “hard coding” for the indexes.

phone_numbers <- c(2,8,1,3,3,0,8,0,0,4)
prefix <- phone_numbers[1:3]
small <- phone_numbers[phone_numbers<=5]
small

## [1] 2 1 3 3 0 0 0 4

large <- phone_numbers[phone_numbers>5]
large

## [1] 8 8

phone_numbers[phone_numbers>5] <- 5
phone_numbers

##  [1] 2 5 1 3 3 0 5 0 0 4

odd_index <- (phone_numbers %%2) != 0
odd_index

##  [1] FALSE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE FALSE FALSE FALSE

phone_numbers[odd_index] <- 0
phone_numbers

##  [1] 2 0 0 0 0 0 0 0 0 4

In the code chunk below:

9. Create a vector of 100 simulated dice rolls called fifty_rolls_1
10. Create a second vector of 100 simulated dice rolls called fifty_rolls_2
11. If you pretend these two die are rolled at the same time, find how many of the 100 two-dice rolls are doubles. (doubles are when the two die have the same number)

# this function makes it so that your "random" number generator is at the same spot as mine. 
set.seed(102389) ## leave this here to keep the randomness consistent
roll_six_sided_die <- function(){
  die_rolls <- 1:6
  die_probs <- c(rep(1/6,6))
  rolls <- sample (die_rolls,1, replace = T, prob = die_probs)
  return(rolls)
}
fifty_rolls_1 <- sapply(1:100,function(x) roll_six_sided_die())
fifty_rolls_1

##   [1] 3 4 2 1 6 3 3 6 5 5 5 1 6 4 4 2 3 5 6 4 5 3 3 2 4 1 2 5 6 6 4 3 3 1 6 5 2
##  [38] 6 1 1 4 2 2 6 1 6 3 5 2 6 3 6 1 5 3 5 4 3 6 1 1 6 3 3 3 4 1 1 2 4 1 1 2 1
##  [75] 2 1 4 1 4 2 1 6 4 1 2 5 3 3 3 4 4 5 6 1 6 1 4 5 3 5

fifty_rolls_2 <- sapply(1:100,function(x) roll_six_sided_die())
fifty_rolls_2

##   [1] 2 1 2 3 4 6 1 4 5 3 1 5 6 6 6 4 2 3 2 2 3 5 2 4 3 6 6 5 5 4 4 6 4 6 5 5 2
##  [38] 3 6 6 1 4 4 6 3 6 4 2 6 5 3 3 4 4 2 1 5 6 2 6 5 5 1 5 1 2 1 6 6 2 6 1 6 1
##  [75] 1 6 4 4 3 5 3 4 6 6 6 5 6 3 4 4 2 4 6 3 1 1 2 1 3 5

double <- sum(fifty_rolls_1 == fifty_rolls_2)
double

## [1] 21

Extra Credit, 5 points:

12. Make a function that does 9, 10, and 11 together for you, and returns the number of doubles. (Note: functions don’t have to have input arguments!)

count_doubles <- function(){
  set.seed(102389)
roll_six_sided_die <- function(){
  die_rolls <- 1:6
  die_probs <- c(rep(1/6,6))
  rolls <- sample (die_rolls,1, replace = T, prob = die_probs)
  return(rolls)
}
fifty_rolls_1 <- sapply(1:100,function(x) roll_six_sided_die())
print(fifty_rolls_1)

fifty_rolls_2 <- sapply(1:100,function(x) roll_six_sided_die())
print(fifty_rolls_2)

double <- sum(fifty_rolls_1 == fifty_rolls_2)
return(double)
}

count_doubles()

##   [1] 3 4 2 1 6 3 3 6 5 5 5 1 6 4 4 2 3 5 6 4 5 3 3 2 4 1 2 5 6 6 4 3 3 1 6 5 2
##  [38] 6 1 1 4 2 2 6 1 6 3 5 2 6 3 6 1 5 3 5 4 3 6 1 1 6 3 3 3 4 1 1 2 4 1 1 2 1
##  [75] 2 1 4 1 4 2 1 6 4 1 2 5 3 3 3 4 4 5 6 1 6 1 4 5 3 5
##   [1] 2 1 2 3 4 6 1 4 5 3 1 5 6 6 6 4 2 3 2 2 3 5 2 4 3 6 6 5 5 4 4 6 4 6 5 5 2
##  [38] 3 6 6 1 4 4 6 3 6 4 2 6 5 3 3 4 4 2 1 5 6 2 6 5 5 1 5 1 2 1 6 6 2 6 1 6 1
##  [75] 1 6 4 4 3 5 3 4 6 6 6 5 6 3 4 4 2 4 6 3 1 1 2 1 3 5

## [1] 21