How to find SubString in R programming?

String Manipulation in detail

In this article, we will explore different ways to find substrings in the R programming language.

R provides multiple methods for substring operations, including:

• Using substr() function
• Using str_detect() function
• Using grep() function

Method 1: Using substr() function

The substr() function in R is used to extract a substring from a given string based on specified start and end positions.

Syntax:

substr(string_name, start, end)

Return Value: This function returns the substring from the given string according to the specified start and end indexes.

Example 1:

Operations on a Single Matrix

R allows element-wise operations on matrices using overloaded arithmetic operators. Let’s look at some examples.

# Given String
text <- "Learning R Programming"

# Using substr() function
result <- substr(text, 1, 8)

print(result)

Example:

# Given String
sentence <- "Data science and machine learning"

# Using substr() function
result <- substr(sentence, 13, 27)

print(result)

Output:

[1] "and machine le"

Method 2: Using str_detect() function

The str_detect() function from the stringr package checks whether a specified substring exists within a string. It returns TRUE if a match is found and FALSE otherwise.

Syntax:

str <- paste(c(2:4), "5", sep = "-")
print(str)

Parameters:

• string: The target string or vector of strings.
• pattern: The substring pattern to be searched.

Example:

# Load library
library(stringr)

# Creating a vector
words <- c("Apple", "Banana", "Cherry", "Mango")

# Pattern to search
pattern <- "Banana"

# Using str_detect() function
str_detect(words, pattern)

Output:

[1] FALSE  TRUE FALSE FALSE

Method 3: Using grep() function

The grep() function returns the indices of elements in a character vector that match a specified pattern. If multiple matches are found, it returns a list of their respective indices.

Syntax:

grep(pattern, string, ignore.case=FALSE)

Parameters:

• pattern: A regular expression pattern to match.
• string: The character vector to search.
• ignore.case: Whether to perform case-insensitive searching (default is FALSE).

Example:

# Define vector
text_values <- c("Orange", "orchestra", "blue", "ocean")

# Using grep() to find pattern "or"
matching_indices <- grep("or", text_values, ignore.case=TRUE)

print(matching_indices)

Output:

[1] 1 2 4