How to Use the str_detect() Function in R

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The str_detect() function from the stringr in R is “used to detect the presence or absence of a specific pattern in a string.”

Syntax

str_detect(string, pattern, negate = FALSE)

Parameters

  1. string: It is a character vector.
  2. pattern: It is the pattern to look for.
  3. negate: If TRUE, return non-matching elements.

Example 1: Using str_detect() function with String

library(stringr)

fruits <- c("apple pie", "banana split", "cherry tart", "apple juice")

result <- str_detect(fruits, "apple")

print(result)

Output

[1] TRUE FALSE FALSE TRUE

Example 2: Using Regular Expressions

You can detect if any strings in a vector start with the letter “a”.

library(stringr)

fruits <- c("apple", "banana", "avocado", "cherry")

result <- str_detect(fruits, "^a")

print(result)

Output

[1] TRUE FALSE TRUE FALSE

Example 3: Case-Insensitive Detection

Detect the word “apple”, irrespective of its case.

library(stringr)

fruits <- c("Apple pie", "banana split", "APPLE juice", "cherry tart")

result <- str_detect(fruits, regex("apple", ignore_case = TRUE))

print(result)

Output

[1] TRUE FALSE TRUE FALSE

Example 4: Using str_detect() with Vector

library(stringr)

# Create a vector of sentences
sentences <- c(
  "The rain in Spain falls mainly on the plain.",
  "It was a sunny day.",
  "Raindrops keep falling on my head.",
  "I don't have an umbrella."
)

# Use str_detect() to find sentences containing the word "rain"
contains_rain <- str_detect(sentences, "rain")

# Print the result
print(contains_rain)

Output

[1] TRUE FALSE FALSE FALSE

Example 5: Using a str_detect() function with Data Frame

# Load the necessary libraries
library(stringr)
library(dplyr) # For data manipulation

# Create a data frame of books
books <- data.frame(
  title = c(
    "The Magic of Thinking Big",
    "How to Win Friends and Influence People",
    "The Magic Mountain",
    "The Art of War",
    "The Secret Magic"
  ),
  author = c(
    "David J. Schwartz",
    "Dale Carnegie",
    "Thomas Mann",
    "Sun Tzu",
    "Unknown"
  )
)

# Use str_detect() to filter rows with
# titles containing the word "magic" (case-insensitive)
magic_books <- books %>%
  filter(str_detect(title, regex("magic", ignore_case = TRUE)))

# Print the result
print(magic_books)

Output

Using a str_detect() function with Data Frame

That’s it!

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