introduction to r programming for data science coursera answers week 3

Practice Quiz

1. Which looping statement should you use if you want to continue to perform an operation if the value of an expression is true?

  • For Each loop
  • For loop
  • Do While loop
  • While loop

2. What happens if a user-defined function is missing the return statement?

  • The function returns an error.
  • The function returns the last evaluated expression in the function.
  • The function returns a NULL value.
  • The function returns the first evaluated expression it encounters and then immediately exits the function.

3. Assume you have a variable called word_string that contains the string “The quick red fox jumped over the lazy dog.” Which function can you use to replace the word “dog” with the word “cat” in the word_string variable?

  • nchar()
  • chartr()
  • strsplit()
  • substr()

4. Which of the following statements about regular expressions are true? Select two answers.

  • Regular expressions perform mathematical operations on numeric values.
  • Regular expressions are used to match patterns in strings and text.

  • Regular expressions evaluate a condition to determine if it is true or false.
  • Regular expressions are primarily used for data extraction.

5. How do you convert a UNIX date/time format to an R Date object?

  • Pass the UNIX date/time value to the as.Date() function.
  • Pass the UNIX date/time value to the as.POSIXct() function and then pass that value to the as.Date() function.
  • Pass the UNIX date/time value to the as.POSIXct() function and then pass that value to the is.Date() function.
  • Pass the UNIX date/time value to the is.Date() function.

6. What type of statement should you add to your code if you know that an error or warning might occur?

  • Incorrect distractor
  • A catchError statement.
  • A tryCatch statement.
  • A tryError statement.

Graded Quiz

7. What is the result of the conditional statement 25 > 15 | 99 >= 100?

  • TRUE
  • FALSE

8. How do you define a global variable in a function?

  • Use the == assignment operator.
  • Use the -> assignment operator.
  • Use the <- assignment operator.
  • Use the <<- assignment operator.

9. You can use the str_sub() function to form a substring by counting back from the last position. This function is part of which package?

  • stringr
  • tidyr
  • readr
  • purrr

10. Assume you have a data frame that contains a string variable called ‘phone’. The phone numbers in this variable appear in (###) ###-#### or ###-###-#### format. Which feature of R can you use to isolate the area code (the three numbers between the parentheses or the first three numbers)?

  • It is not possible to do this using R.
  • A string operation.
  • A mathematical operation.
  • A regular expression.

11. When you convert a date in string format to a Date object, what information do you need to pass to the as.Date() function? Select two answers.

  • The UNIX format of the string.
  • The number of days since January 1, 1970.
  • The date format of the string.

  • The string containing the date.

12. What is the difference between an error and a warning in you R code?

  • You can catch a warning, but you cannot catch an error.
  • An error halts code execution, while a warning does not.
  • A warning halts code execution, while an error does not.
  • You can catch an error, but you cannot catch a warning.

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