PA 9: Writing Functions

Author

Instructions

You will write several small functions, then use them to unscramble a message. Many of the functions have been started for you below, but none of them are complete as is.

This task is complex. It requires many different types of abilities. Everyone will be good at some of these abilities but nobody will be good at all of them. In order to produce the best product possible, you will need to use the skills of each member of your group.

1. Write code to manipulate the vector of numbers nums. Your code should divide each element in the vector by the smallest element and round the results to the nearest whole number. Hint: This code should not be a function. Consider using the existing functions round() and min() and don’t forget to account for NA values.

nums <- 3:12

2. Turn your code from Q1 into a function called divide_and_round(). Fill in the skeleton code below.

divide_and_round <- function(vec){

}

3. Test your function by running the code below.

test <- c(5:10, NA)
divide_and_round(test)  #you should see mostly values of 1 and 2, plus an NA

NULL

4. Write code to manipulate the vector of numbers nums. Your code should, for each element, return TRUE if the number is NOT divisible by 9 OR 12, and return FALSE otherwise. Hint: This code should not be a function. Note - the function %% is handy here - look it up if you do not know what it does.

ifelse(nums %% 9 == 0 ___ nums %% 12 == 0, ____ , ____)  #it should say FALSE for 9 and 12 positions

Error in parse(text = input): <text>:1:23: unexpected input
1: ifelse(nums %% 9 == 0 _
                          ^

5. Turn your code from Q4 into a function called no_nines_or_twelves().

no_nines_or_twelves <- function(vec) {

}

6. Test your function by running the code below.

test <- c(seq(from = 15, to = 60, by = 5), NA)
test

 [1] 15 20 25 30 35 40 45 50 55 60 NA

no_nines_or_twelves(test)  #45 and 60 should have FALSE in their positions and NA in the last

NULL

7. Write a function called every_other(). This function should take in a vector and return every other value in the vector. Include an optional argument called start which lets you choose where to start skipping; that is, if start = 1, the function returns the 1st, 3rd, 5th, etc. values and if start = 2, the function returns the 2nd, 4th, 6th, etc. values.

Hint: Do not use a for() loop to do this! Accomplish this with the seq_along() function, bracket subsetting ([]), and modulus arithmetic (%%).

# the following identify if a value is even or odd
(seq_along(nums)) %% 2 == 0

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

(seq_along(nums)) %% 2 > 0

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

# using [] to subset will keep values with TRUE in that element's position

nums[(seq_along(nums)) %% 2 == 0]  #should return even numbers

[1]  4  6  8 10 12

nums[(seq_along(nums)) %% 2 > 0]  #should return odd numbers

[1]  3  5  7  9 11

Fill in the skeleton below. Remember the default should be start as 1.

every_other <- function(vec, _________){
  
  if (start == 2) {
    vec[]
  } 
  
  else if (start == 1) {
    vec[]
  }

}

Error in parse(text = input): <text>:1:30: unexpected input
1: every_other <- function(vec, _
                                 ^

8. Test your function by running the code below.

test <- c(1:10)

every_other(test, start = 1) #return odds

Error in every_other(test, start = 1): could not find function "every_other"

every_other(test, start = 2) #return evens

Error in every_other(test, start = 2): could not find function "every_other"

9. Write a function called shorten(). This function should take in a vector, drop all values BEFORE the cumulative sum is greater than a provided number, and return the remaining values from the original vector.

Hint: Do not use a while() loop to do this! Accomplish this with the cumsum() function and bracketing.

Here is an example of testing if the cumulative sum is greater than or equal to 30.

# look at the following - which completes the task needed
cumsum(nums)

 [1]  3  7 12 18 25 33 42 52 63 75

cumsum(nums) >= 30

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

nums[cumsum(nums) >= 30]  #returns only numbers 8+

[1]  8  9 10 11 12

shorten <- function(x, sum){

}

10. Test your function by running the code below.

test <- 20:50 
shorten(test, 350) #should be 33+

NULL

11. Once you have written your four functions correctly, run the following code:

#remember to use the green arrow to run the whole code chunk
my_vec <- c(39, 1.87, 48, 11, 8, 45, 21, 5, 12, 33, 9, 11, 108,
            4, 18, 5, 16, 17, 8, 48, 27, 24, 4, 22, 12, 27, 23,
            46, 42, 35, 15, 34, 36, 26, 18, 10, 18.21, 72.04,
            36.9, 41.81, 29, 89.75, 34.03, 20.18, 48.74, 15.76,
            31.86, 83.6, 43.55, 39.99, 23.55, 8.54, 24.71, 22.02,
            9.71, 62.14, 35.46, 16.61, 15.66, 21.29, 30.52,
            201.07, 45.81, 7.85, 30.13, 34.14, 22.62, 10.2, 6.02,
            30.12, 10.64, 31.72, 24.57, 14.43, 43.37, 89.93,
            44.72, 51.32, 13.62, 45.56, 22.96, 7.05, 29.99, 41.38,
            26.59, 23.04, 19.82, 50.73, 39.56, 43.79, 30.22, 85.85,
            5.78, 78.85, 29.52, 66.27, 44.06, 27.28, 24.43, 64.32,
            3.35, 67.45, 46.72, 48.44, 48.65, 33.3, 40.28, 19.04)

my_vec <- every_other(my_vec, start = 2)

Error in every_other(my_vec, start = 2): could not find function "every_other"

# Should have 54 elements! 

my_vec <- divide_and_round(my_vec)

my_vec <- every_other(my_vec, start = 1)

Error in every_other(my_vec, start = 1): could not find function "every_other"

# Should have 27 elements!

my_vec <- shorten(my_vec, 350)
# Should have 12 elements!

my_vec <- my_vec[no_nines_or_twelves(my_vec)]
# Should have 6 elements! 

my_vec <- sort(my_vec)

my_vec

NULL

Canvas Submission

If you have done everything correctly, your final vector will be six numbers long. Google these six numbers to find a TV show they are famously associated with as your final answer and submit to Canvas.

--- title: "PA 9: Writing Functions" author: "Instructions" format: html: embed-resources: true code-tools: true toc: true editor: source execute: error: true echo: true --- You will write several small functions, then use them to unscramble a message. Many of the functions have been started for you below, but **none** of them are complete as is. ***This task is complex. It requires many different types of abilities. Everyone will be good at some of these abilities but nobody will be good at all of them. In order to produce the best product possible, you will need to use the skills of each member of your group.***  **1. Write code to manipulate the vector of numbers `nums`. Your code should divide each element in the vector by the smallest element and round the results to the nearest whole number.** Hint: This code should not be a function. Consider using the existing functions `round()` and `min()` and don't forget to account for `NA` values. ```{r} #| label: q1 nums <- 3:12 ``` **2. Turn your code from Q1 into a function called `divide_and_round()`.** Fill in the skeleton code below. ```{r} #| label: q2 divide_and_round <- function(vec){ } ``` **3. Test your function by running the code below.** ```{r} #| label: q3 test <- c(5:10, NA) divide_and_round(test) #you should see mostly values of 1 and 2, plus an NA ```  **4. Write code to manipulate the vector of numbers `nums`. Your code should, for each element, return `TRUE` if the number is NOT divisible by 9 OR 12, and return `FALSE` otherwise.** Hint: This code should not be a function. Note - the function `%%` is handy here - look it up if you do not know what it does. ```{r} #| label: q4 ifelse(nums %% 9 == 0 ___ nums %% 12 == 0, ____ , ____) #it should say FALSE for 9 and 12 positions ``` **5. Turn your code from Q4 into a function called `no_nines_or_twelves()`.** ```{r} #| label: q5 no_nines_or_twelves <- function(vec) { } ``` **6. Test your function by running the code below.** ```{r} #| label: q6 test <- c(seq(from = 15, to = 60, by = 5), NA) test no_nines_or_twelves(test) #45 and 60 should have FALSE in their positions and NA in the last ```  **7. Write a function called `every_other()`. This function should take in a vector and return every other value in the vector. Include an optional argument called `start` which lets you choose where to start skipping; that is, if `start = 1`, the function returns the 1st, 3rd, 5th, etc. values and if `start = 2`, the function returns the 2nd, 4th, 6th, etc. values.** Hint: **Do not** use a `for()` loop to do this! Accomplish this with the `seq_along()` function, bracket subsetting (`[]`), and modulus arithmetic (`%%`). ```{r} #| label: help-code-q7 # the following identify if a value is even or odd (seq_along(nums)) %% 2 == 0 (seq_along(nums)) %% 2 > 0 # using [] to subset will keep values with TRUE in that element's position nums[(seq_along(nums)) %% 2 == 0] #should return even numbers nums[(seq_along(nums)) %% 2 > 0] #should return odd numbers ``` Fill in the skeleton below. Remember the default should be `start` as 1. ```{r} #| label: q7 every_other <- function(vec, _________){ if (start == 2) { vec[] } else if (start == 1) { vec[] } } ``` **8. Test your function by running the code below.** ```{r} #| label: q8 test <- c(1:10) every_other(test, start = 1) #return odds every_other(test, start = 2) #return evens ```  **9. Write a function called `shorten()`. This function should take in a vector, drop all values BEFORE the cumulative sum is greater than a provided number, and return the remaining values from the original vector.** Hint: **Do not** use a `while()` loop to do this! Accomplish this with the `cumsum()` function and bracketing. Here is an example of testing if the cumulative sum is greater than or equal to 30. ```{r} #| label: help-q9 # look at the following - which completes the task needed cumsum(nums) cumsum(nums) >= 30 nums[cumsum(nums) >= 30] #returns only numbers 8+ ``` ```{r} #| label: q9 shorten <- function(x, sum){ } ``` **10. Test your function by running the code below.** ```{r} #| label: q10 test <- 20:50 shorten(test, 350) #should be 33+ ``` **11. Once you have written your four functions correctly, run the following code:** ```{r} #| label: q11 #remember to use the green arrow to run the whole code chunk my_vec <- c(39, 1.87, 48, 11, 8, 45, 21, 5, 12, 33, 9, 11, 108, 4, 18, 5, 16, 17, 8, 48, 27, 24, 4, 22, 12, 27, 23, 46, 42, 35, 15, 34, 36, 26, 18, 10, 18.21, 72.04, 36.9, 41.81, 29, 89.75, 34.03, 20.18, 48.74, 15.76, 31.86, 83.6, 43.55, 39.99, 23.55, 8.54, 24.71, 22.02, 9.71, 62.14, 35.46, 16.61, 15.66, 21.29, 30.52, 201.07, 45.81, 7.85, 30.13, 34.14, 22.62, 10.2, 6.02, 30.12, 10.64, 31.72, 24.57, 14.43, 43.37, 89.93, 44.72, 51.32, 13.62, 45.56, 22.96, 7.05, 29.99, 41.38, 26.59, 23.04, 19.82, 50.73, 39.56, 43.79, 30.22, 85.85, 5.78, 78.85, 29.52, 66.27, 44.06, 27.28, 24.43, 64.32, 3.35, 67.45, 46.72, 48.44, 48.65, 33.3, 40.28, 19.04) my_vec <- every_other(my_vec, start = 2) # Should have 54 elements! my_vec <- divide_and_round(my_vec) my_vec <- every_other(my_vec, start = 1) # Should have 27 elements! my_vec <- shorten(my_vec, 350) # Should have 12 elements! my_vec <- my_vec[no_nines_or_twelves(my_vec)] # Should have 6 elements! my_vec <- sort(my_vec) my_vec ``` ### Canvas Submission If you have done everything correctly, your final vector will be six numbers long. Google these six numbers to find a TV show they are famously associated with as your final answer and submit to Canvas.