We often come across a functionality where we want to check something by comparing it with patten. We use a regular expression to match certain character vectors in the string. Let’s see how to use regular expression in R.
grepl in R
The grepl() is a built-in function that searches for matches of a string or string vector. It returns TRUE if a string contains the pattern, otherwise FALSE. If the parameter is a string vector, it returns a logical vector (match or not for each vector element). It stands for “grep logical”.
To find a pattern in string or string vector, use the grepl() function. In their most basic form, regular expressions can be used to see whether a pattern exists inside a character string or a vector of character strings.
grepl(pattern, x, ignore.case = FALSE, perl = FALSE, fixed = FALSE, useBytes = FALSE)
pattern: It is a regular expression or string for fixed=TRUE
x: It is a string, the character vector
perl: It is logical. Should Perl-compatible regexps be used? Has priority overextended.
fixed: It is logical. If the TRUE, the pattern is a string to be matched as is. Overrides all conflicting arguments
useBytes: It is logical. If TRUE, the matching is done byte-by-byte rather than character-by-character.
Both functions need a pattern and an x argument, where the pattern is the regular expression you want to match for, and the x argument is the character vector from which matches should be sought.
sv <- "Infosys is currently trading at 1435 Rs." op <- grepl("\\d+", sv) print(op)
In this example, we are searching if the string vector contains a numeric value or not. It returns TRUE because it contains the numeric value.
That is it for this tutorial.