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Function definition

A function is a component of the SAS programming language that can accept input, perform a computation or other operation, and return a value

Where can a SAS function can be used?

in data step programming
in a WHERE expression (where statement or where clause)
in proc sql

What is a character function?

A SAS function that returns information based on character data is called a character function

Character functions that converts the case of characters

Function	Defintion
UPCASE	Upcase function is used for converting english alphabet letters of a variable's value to uppercase
LOWCASE	Lowcase function is used for convering englight alphabet letters of a variable's value to lowercase
PROPCASE	Propcase function is used for converting all words of a variable's value to proper case. That is, propcase function converts the first letter of each 'word' to uppercase (and other letters of the word to lowercase). By default these characters are considered word separators: blank, forward slash, hyphen, open parenthesis, period

Create sample data

data case01;
   infile datalines truncover;
   input string $50.;
   obs=_n_;
datalines;
www.google.com
your name is Alfred
His Name is John
TREATMENT 1
aDverSE event
Con(med
Con)med
;
run;

Create 3 new variables named upper, lower and proper by appying upcase, lowcase and propcase functions respectively on sring variable

As the returned values from the functions are assigned to new variables here, the original variable values remain unaltered
Notice that in the newly created upper variable, on all observations all the alphabets have been converted to uppercase
Notice that in the newly created lower variable, on all observations all the alphabets have been converted to lowercase
Notice that in the newly created proper variable, on observations where each word is separated by a space,period,open parenthesis, the first letter of the word is converted to uppercase and other letters of the word are converted to lowercase. On observation 7, the first letter of text 'med' is not converted to uppercase because a closing parenthesis is not considered as a word separator and hence entire text 'con)med' is considered as single word

data case02;
   set case01;
   upper=upcase(string);
   lower=lowcase(string);
   proper=propcase(string);
run;

Character Functions that return the length of the strings

Function	Definition
LENGTH	Length function is used for obtaining the number of characters in a character string excluding trailing blanks, retruns a value of 1 for a blank value
LENGTHN	LengthN function is used for obtaining the number of characters in a character string excluding trailing blanks, retruns 0 for blank value

Create sample data

data lengths01;
   infile datalines truncover;
   input string $50.;
datalines;
google
google.com
google  .com
 
www.google.com
g
;
run;

Create two new variables length and lengthn by obtaining the length of string variable using LENGTH and LENGTHN functions

Notice in the output that both length and lengthn returns the same value on all observations except 4th observation where string variable has a null value. As described in definition, Length function returns 1 for null string and LengthN function returns 0 null string
So, caution should be exercised when LENGTH function is used to identify a null string as it returns a value of 1 when there is one character in the value or the string is null.

data lengths02;
   set lengths01;
   length=length(string);
   lengthn=lengthn(string);
run;

Character function to extract words from a string

Function	Definition
SCAN	The SCAN function extracts a specified word from a character string. A word is a sequence of characters separated by delimiters. By default, these characters are considered delimiters: blank, !, $, %, &, (, ), *, +, ,, -, ., /, ;, <, ^, \|.

Create sample data

data scan_example;
   infile datalines truncover;
   input string $50.;
   obs=_n_;
datalines;
Hello World
SAS!Programming$Language
Data-Analysis in Healthcare
Open(Source)Tools
;
run;

Create new variables to extract specific words using SCAN function

The SCAN function allows extracting specific words by their position from the string variable.
Words are identified based on delimiters. By default, the following characters are used as delimiters: blank, !, $, %, &, (, ), *, +, ,, -, ., /, ;, <, ^, |.
Notice how the extracted word depends on the position provided as the second argument to the SCAN function. If the position exceeds the number of words, the function returns a missing value.
You can override the default delimiters by specifying your own set of delimiters in the third argument.

data scan_result;
   set scan_example;
   first_word = scan(string, 1); /* Extract the first word */
   second_word = scan(string, 2); /* Extract the second word */
   third_word = scan(string, 3); /* Extract the third word */
   custom_word = scan(string, 2, "()"); /* Specify custom delimiters */
run;

Character function to extract or modify parts of a string

Function	Definition
SUBSTR	The SUBSTR function is used to extract a substring from a character string, starting at a specified position for a specified length. It can also be used to replace part of a string by assigning a value to a substring.

Create sample data

data substr_example;
   infile datalines truncover;
   input string $50.;
   obs=_n_;
datalines;
Hello World
SAS Programming
Data Science and Analytics
1234567890
;
run;

Extract and modify parts of a string using SUBSTR function

The SUBSTR function extracts a portion of a string based on the starting position and length specified.
If the length is omitted, the function extracts from the starting position to the end of the string.
SUBSTR can also be used on the left side of an assignment statement to modify a part of the string.

data substr_result;
   set substr_example;
 
   /* Extract parts of the string */
   first_5_chars = substr(string, 1, 5); /* Extract the first 5 characters */
   from_7_to_end = substr(string, 7); /* Extract from the 7th character to the end */
 
   /* Modify parts of the string */
   modified_string = string;
   substr(modified_string, 7, 5) = "#####"; /* Replace 5 characters starting at position 7 */
run;

Character function to find the position of a substring in a string

Function	Definition
FIND	The FIND function returns the position of the first occurrence of a substring within a character string. It includes options to ignore case sensitivity or specify a starting position. If the start position is negative, the search begins at that position and proceeds backwards through the string.

Create sample data

data find_example;
   infile datalines truncover;
   input string $50.;
   obs=_n_;
datalines;
Hello World
Welcome to SAS
Data Analytics is Amazing
HELLO AGAIN
Find the Needle in the Haystack
;
run;

Find the position of a substring using FIND function

The FIND function locates the starting position of the specified substring in a character string.
The function is case-sensitive by default, but you can use the 'i' modifier to ignore case.
To search backwards, provide a negative start position. For example, -10 means the search starts at the 10th position from the end of the string and proceeds backward.
If the substring is not found, the function returns 0.

Example 1: Basic Usage

data find_basic;
   set find_example;
   pos_hello = find(string, 'Hello'); /* Find the position of 'Hello' */
   pos_sas = find(string, 'SAS'); /* Find the position of 'SAS' */
run;

Example 2: Using 'i' Modifier to Ignore Case

data find_ignore_case;
   set find_example;
   pos_ignore_case = find(string, 'hello', 'i'); /* Ignore case while finding 'hello' */
run;

Example 3: Using a Negative Start Position for Reverse Search

data find_reverse;
   set find_example;
   pos_reverse_10 = find(string, 'the', -10); /* Start searching for 'the' from the 10th position from the end and proceed backward */
   pos_reverse_end = find(string, 'the', -length(string)); /* Start searching from the rightmost position (end of the string) */
run;

Example 4: Combining Modifiers and Start Position

data find_combined;
   set find_example;
   pos_combined = find(string, 'hello', 'i', -10); /* Ignore case and search starting from the 10th position from the end */
run;

Character Functions to Count Substrings, Characters, and Words

Function	Definition
COUNT	The COUNT function counts the number of times a specified substring appears in a character string. The search is case-sensitive by default.
COUNTC	The COUNTC function counts the number of specific characters that appear in a character string. It allows for multiple characters to be counted at once.
COUNTW	The COUNTW function counts the number of words in a character string. Words are defined as sequences of characters separated by delimiters. By default, delimiters include spaces, punctuation marks, and other special characters.

Create sample data

data counts01;
   infile datalines truncover;
   input string $50.;
datalines;
Welcome to SAS!
Hello, SAS! Welcome.
Count the number of words.
SAS, Programming, Analytics.
SAS SAS SAS
;
run;

Create variables count_substring, count_characters, and count_words using COUNT, COUNTC, and COUNTW functions

COUNT: Notice in the output that the COUNT function counts the number of occurrences of the specified substring in the string. For example, it counts the number of times "SAS" appears.
COUNTC: The COUNTC function counts the number of times specific characters appear in the string. For example, it can count the number of commas, spaces, or any other characters.
COUNTW: The COUNTW function counts the number of words in the string based on the default or specified delimiters. For example, it identifies words separated by spaces or commas.
The case sensitivity in COUNT and COUNTC can be adjusted using modifiers such as 'i' to ignore case.

data counts02;
   set counts01;
 
   /* Count the number of times "SAS" appears */
   count_substring = count(string, 'SAS');
 
   /* Count the number of spaces in the string */
   count_spaces = countc(string, ' ');
 
   /* Count the number of words in the string */
   count_words = countw(string);
run;

Character Function to Replace Substrings in Clinical Trials Data

Function	Definition
TRANWRD	The TRANWRD function replaces all occurrences of a specified substring within a character string with another substring. This function is useful in clinical trials data to standardize variable values or correct data inconsistencies.

Create sample clinical trials data

data clinical_data01;
   infile datalines truncover;
   input patient_id $30. visit_desc $50.;
datalines;
001 Screening Visit
002 Baseline Visit
003 Followup Visit 1
004 Followup Visit 2
005 End of Study
006 Baseline
007 Followup Visit
;
run;

Standardize visit descriptions using TRANWRD function

The TRANWRD function is used here to standardize the visit descriptions in the `visit_desc` variable.
For example, the word "Followup" is replaced with "Follow-Up" to ensure consistent terminology across the dataset.
The function is also used to expand abbreviations like "EOS" to "End of Study" (if applicable).

data clinical_data02;
   set clinical_data01;
 
   /* Replace "Followup" with "Follow-Up" */
   visit_desc_std1 = tranwrd(visit_desc, 'Followup', 'Follow-Up');
 
   /* Replace "Baseline" with "Baseline Visit" for consistency */
   visit_desc_std2 = tranwrd(visit_desc_std1, 'Baseline', 'Baseline Visit');
run;

Character Function to Remove or Retain Specific Characters in Strings

Function	Definition
COMPRESS	The COMPRESS function removes specific characters from a character string. It can also be used to retain specific characters by using the optional `modifiers` argument. The 'k' modifier (keep) is combined with other modifiers (e.g., 'd' for digits) to retain specific characters.

Create sample data

* Create a dataset with raw strings containing various characters ;
data compress_data01;
   infile datalines truncover;
   input raw_string $50.;
datalines;
123-456-7890
Address: 123 Main St.
Order#12345
This is a test!
2023/04/15
hello-world_2023
;
run;

Examples for removing specific characters using COMPRESS function

The COMPRESS function is used to remove unwanted characters by specifying them explicitly in the second argument.
In the examples below, characters like punctuation marks, special symbols, or specific letters are removed.

* Remove specific characters from the strings ;
data compress_remove;
   set compress_data01;
 
   * Remove all punctuation marks (e.g., ',', '.', '!', etc.) ;
   no_punctuation = compress(raw_string, ',.!?-_/');
 
   * Remove specific characters (e.g., numbers) ;
   remove_digits = compress(raw_string, '0123456789');
 
   * Remove vowels (a, e, i, o, u) ;
   remove_vowels = compress(raw_string, 'aeiouAEIOU');
run;

Examples for retaining specific characters using COMPRESS function

The COMPRESS function is used to retain specific characters by using the 'k' modifier (keep) combined with other options such as 'd' (digits) or 'a' (alphabets).
In the examples below, numeric digits are extracted using 'kd', and other specific characters like alphabets and underscores are retained for standardization.

 
* Retain specific characters in the strings ;
data compress_keep;
   set compress_data01;
 
   * Keep only digits using 'kd' ;
   digits_only = compress(raw_string, , 'kd');
 
   * Retain only alphabets using 'ka' ;
   alphabets_only = compress(raw_string, , 'ka');
 
   * Retain only specific characters: alphabets, digits, and underscores ;
   standardized_string = compress(raw_string, ' _', 'kad');
run;