How to Check if a Column Contains a String in R
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
Introduction
Whether you’re doing some data cleaning or exploring your dataset, checking if a column contains a specific string can be a crucial task. Today, I’ll show you how to do this using both str_detect() from the stringr package and base R methods. We’ll also tackle finding partial strings and counting occurrences. Let’s dive right in!
Using str_detect from stringr
First, we’ll use the str_detect function. The stringr package is part of the tidyverse collection, which brings a set of user-friendly functions to text manipulation. We’ll start by ensuring it’s installed and loaded:
install.packages("stringr")
Now, let’s create a sample dataset:
library(stringr)
# Sample data
data <- data.frame(
name = c("Alice", "Bob", "Carol", "Dave", "Eve"),
description = c("Software developer", "Data analyst", "UX designer", "Project manager", "Data scientist")
)
data
name description 1 Alice Software developer 2 Bob Data analyst 3 Carol UX designer 4 Dave Project manager 5 Eve Data scientist
Examples
Using stringr
Check for Full String
Suppose we want to check if any of the description column contains “Data analyst”:
# Detect if 'description' contains 'Data analyst' data$has_data_analyst <- str_detect(data$description, "Data analyst") print(data)
name description has_data_analyst 1 Alice Software developer FALSE 2 Bob Data analyst TRUE 3 Carol UX designer FALSE 4 Dave Project manager FALSE 5 Eve Data scientist FALSE
In the output, the has_data_analyst column will be TRUE for “Bob” and FALSE for others.
Check for Partial String
Let’s expand our search to any string containing “Data”:
# Detect if 'description' contains any word with 'Data' data$has_data <- str_detect(data$description, "Data") print(data)
name description has_data_analyst has_data 1 Alice Software developer FALSE FALSE 2 Bob Data analyst TRUE TRUE 3 Carol UX designer FALSE FALSE 4 Dave Project manager FALSE FALSE 5 Eve Data scientist FALSE TRUE
This will show TRUE for “Bob” and “Eve,” where both “Data analyst” and “Data scientist” are detected.
Count Occurrences
If you need to count how many times “Data” appears, use str_count:
# Count occurrences of 'Data' data$data_count <- str_count(data$description, "Data") print(data)
name description has_data_analyst has_data data_count 1 Alice Software developer FALSE FALSE 0 2 Bob Data analyst TRUE TRUE 1 3 Carol UX designer FALSE FALSE 0 4 Dave Project manager FALSE FALSE 0 5 Eve Data scientist FALSE TRUE 1
This will add a column data_count with the exact count of occurrences per row.
Using Base R
For those who prefer base R, the grepl and gregexpr functions can help.
Check for Full or Partial String
grepl is ideal for checking if a string is present:
# Using grepl for full/partial string detection
data$has_data_grepl <- grepl("Data", data$description)
print(data)
name description has_data_analyst has_data data_count has_data_grepl 1 Alice Software developer FALSE FALSE 0 FALSE 2 Bob Data analyst TRUE TRUE 1 TRUE 3 Carol UX designer FALSE FALSE 0 FALSE 4 Dave Project manager FALSE FALSE 0 FALSE 5 Eve Data scientist FALSE TRUE 1 TRUE
This will yield the same output as str_detect.
Count Occurrences
For counting occurrences, gregexpr is helpful:
# Count occurrences using gregexpr
matches <- gregexpr("Data", data$description)
data$data_count_base <- sapply(
matches,
function(x) ifelse(x[1] == -1, 0, length(x))
)
print(data)
name description has_data_analyst has_data data_count has_data_grepl 1 Alice Software developer FALSE FALSE 0 FALSE 2 Bob Data analyst TRUE TRUE 1 TRUE 3 Carol UX designer FALSE FALSE 0 FALSE 4 Dave Project manager FALSE FALSE 0 FALSE 5 Eve Data scientist FALSE TRUE 1 TRUE data_count_base 1 0 2 1 3 0 4 0 5 1
This will add a new data_count_base column containing the count of “Data” in each row.
Give It a Try!
The best way to master string detection in R is to experiment with different patterns and datasets. Whether you use str_detect, grepl, or any other approach, you’ll find plenty of ways to customize the search. Try it out with your own datasets, and soon you’ll be searching like a pro!
R-bloggers.com offers daily e-mail updates about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.