Combining with stringr functions

You can pass a regular expression as the pattern argument to any stringr function that has the pattern argument. You can use str_detect() to get a logical vector for whether there was a match, str_subset() to return just the strings with matches, and str_count() to count the number of matches in each string.

As a reminder, compare the output of those three functions with our "c_t" pattern from the previous exercise:

x <- c("cat", "coat", "scotland", "tic toc")
pattern <- "c" %R% ANY_CHAR %R% "t"
str_detect(x, pattern)
str_subset(x, pattern)
str_count(x, pattern)

It now also makes sense to add str_extract() to your repertoire. It returns just the part of the string that matched the pattern:

str_extract(x, pattern)

You'll combine your regular expression skills with stringr to ask how often a q is followed by any character in boy names.

It's always a good idea to test your pattern, so this pattern is shown matched with four names. The first two shouldn't have matches (can you explain why?) but the last two should.

1
- Find the boy_names with the pattern by using str_subset(). Assign the result to names_with_q.
- Run length() on the result to find out how many there are.
2
- Find just the part of boy_names that matched with str_extract(). Assign the result to part_with_q.
- Run table() on the result to find out how many have qu and how many have other patterns.
3
- Check that there weren't any boy_names that might have had the pattern twice (you would have only found the first match) by using str_count(). Assign the result to count_of_q.
- Use table() on the result.
4
- Get a logical vector of whether or not each boy's name contains q* by calling str_detect(). Assign the result to with_q.
- Count the fraction of boy's names containing q* by calculating the mean() of with_q.

Exercise

Combining with stringr functions

Instructions 1/4