The strsplit() in R programming language function is used to split the elements of the specified character vector into substrings according to the given substring taken as its parameter.

The strsplit() function in R is used to split a string into multiple substrings based on a specified separator or pattern. This function takes two arguments: the first argument is the input string and the second argument is the separator or pattern to use for splitting the string.

The separator can be a single character or a regular expression pattern. When a single character is used as the separator, the function splits the string wherever it finds the character. For example, the following code splits the string "Hello, world!" into two substrings, "Hello" and " world!" using a comma (",") as the separator: 

strsplit("Hello, world!", ",")

On the other hand, if a regular expression pattern is used as the separator, the function splits the string wherever it finds a match for the pattern. For example, the following code splits the string "A1B2C3D4" into four substrings, "A", "B", "C", and "D" using a regular expression pattern that matches any digit: 

strsplit("A1B2C3D4", "[0-9]")

The strsplit() function returns a list of substrings, each of which is a character vector. To access individual substrings, you can use list indexing or the unlist() function to convert the list to a vector.