Putting strings together with stringr
For your first stringr function, we'll look at str_c(), the c is short for concatenate, a function that works like paste(). It takes vectors of strings as input along with sep and collapse arguments.
There are two key ways str_c() differs from paste(). First, the default separator is an empty string, sep = "", as opposed to a space, so it's more like paste0(). This is an example of a stringr function, performing a similar operation to a base function, but using a default that is more likely to be what you want. Remember in your pizza order, you had to set sep = "" multiple times.
The second way str_c() differs to paste() is in its handling of missing values. paste() turns missing values into the string "NA", whereas str_c() propagates missing values. That means combining any strings with a missing value will result in another missing value.
Let's explore this difference using your pizza order from the previous chapter.
This is a part of the course
“String Manipulation with stringr in R”
Exercise instructions
We've set up a new my_toppings vector that has a few missing values and taken the first step of creating our order.
- Print
my_toppings_andto see whatpaste()did with the missing values. - Repeat the
paste()statement but instead usestr_c(). You can save some typing by leaving offsep = ""since that is the default. Call this stringmy_toppings_str. - Print
my_toppings_strto see whatstr_c()does with the missing values. - Take the next step in our order, by using
paste()onmy_toppings_andwithcollapse = ", ". - Take the next step in our order, by using
str_c()onmy_toppings_strwithcollapse = ", ". See the difference: just oneNAwill make our entire resultNA.
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
library(stringr)
my_toppings <- c("cheese", NA, NA)
my_toppings_and <- paste(c("", "", "and "), my_toppings, sep = "")
# Print my_toppings_and
___
# Use str_c() instead of paste(): my_toppings_str
my_toppings_str <- ___
# Print my_toppings_str
___
# paste() my_toppings_and with collapse = ", "
___
# str_c() my_toppings_str with collapse = ", "
___
This exercise is part of the course
String Manipulation with stringr in R
Learn how to pull character strings apart, put them back together and use the stringr package.
Time to meet stringr! You'll start by learning about some stringr functions that are very similar to some base R functions, then how to detect specific patterns in strings, how to split strings apart and how to find and replace parts of strings.
Exercise 1: Introducing stringrExercise 2: Putting strings together with stringrExercise 3: String lengthExercise 4: Extracting substringsExercise 5: Hunting for matchesExercise 6: Detecting matchesExercise 7: Subsetting strings based on matchExercise 8: Counting matchesExercise 9: Splitting stringsExercise 10: Parsing strings into variablesExercise 11: Some simple text statisticsExercise 12: Replacing matches in stringsExercise 13: Replacing to tidy stringsExercise 14: ReviewExercise 15: Final challengesWhat is DataCamp?
Learn the data skills you need online at your own pace—from non-coding essentials to data science and machine learning.