Additional Resources:

Run the code below to load the congress dataframe we will use in this quiz



1. In your own words, describe what a function is and provide one example of how you might use it in a data science.

2. Packages in R can contain many useful functions/commands. If you didn’t know what a certain function did, or how it worked, where within RStudio would you look to learn more / see example code? Where would you look outside RStudio?

3. Write a function that takes a character vector as an argument and returns a character vector containing the first letters of each element in the original vector. To show that it works, test it on the character vector sentence defined below.

sentence <- c('you', 'only', 'understand', 'data', 'if', 'data', 'is', 'tidy')
# your answer here

4. Create your own function which accepts a birthyear vector and returns an approximate current age, then use it on the birthyear column of the congress dataframe to create a new age column with mutate.

Note: functions used inside mutate accept single columns from the original dataframe and return a column or vector of the same size. This is a valuable tool for developing your workflow.

5. Write a function that accepts a date string and returns the day of the week it corresponds to, then use it to create a new column of congress representing the weekday of the birth of each politician using mutate.

6. Write a function that accepts a dataframe with the columns birthday and full_name, and prints the names and ages of the k oldest representatives in congress (i.e. not including senators) using a “for loop”. In this sense, k is an arbitrary number that should be given as an argument to the function - set the default value to be 5. If you use the dataframe as the first argument, you can use the pipe operator (“%>%”) to pass the dataframe directly to the function. Define your function such that you can use it like this: congress %>% print_oldest(3).

7. Starting with the function from the previous question, change it such that if k > 5, it only prints the first 5. Test isusing this code: congress %>% print_oldest(100).

Thanks to Devin Cornell and Taylor Brown for helping to create these quizzes!