When grep() should be used?

Q: When grep() should be used?

This grepl() function in the R language returns the value True if the specified pattern is found in the vector and false if it is not found.

Difference between grep() and grepl()

When grepl() should be used?

grep is preferred to opt select columns based on the name of the column.

Example: In this example, we have selected entire columns having the character ‘S’ in the header name.

R

library(dplyr) 
  
# creating a data frame 
df <- data.frame(Department = c('CSE', 'IT', 
                                'ECE', 'EE',  
                                'ME'), 
                 Strength = c(80, 76, 75, 65, 70), 
                 Score = c(75, 70, 65, 60, 60)) 
  
# select columns that contain the string  
# 'S' in their name 
df %>% select(grep('S', colnames(df)))

Output:

Count the Number of Rows that Contain a Certain String. grep() function should be used to count the number of rows in the given data frame that matches with a certain string.

Example: In this example, we have counted the number of rows, in which the header has ‘S’ in it.

R

library(dplyr) 
  
# creating a data frame 
df <- data.frame(Department = c('CSE', 'IT', 'ECE', 
                                'EE', 'ME'), 
                 Strength = c(80, 76, 75, 65, 70), 
                 Score = c(75, 70, 65, 60, 60)) 
  
# select and count columns that contain 
# the string 'S' in their name 
df %>% length(grep('S', colnames(df)))