SAS: How to extract last N characters / digits

This tutorial explains how to extract last N characters or digits of a variable in SAS, along with examples.

In MS Excel, it is easily possible with the RIGHT() function but there is no built-in function to do it in SAS. The RIGHT() function of SAS is used for something else i.e. it right aligns string or character value.

Example 1 : Extract last 4 characters

Suppose you have a product ID in which last 4 characters refers to a product category so you are asked to pull product category information.

data example;
productID = "AB123ZX253";
run;


data example;
set example;
referenceid = substr(productID,length(productID)-3,4);
run;

The output is shown in the image below -

Explanation

The SUBSTR() function returns sub-string from a character variable.

= SUBSTR(character-variable, beginning-position, number-of-characters-to-pull)

The LENGTH() function returns the length of a character variable. In this case, it is 10 characters long. The calculated SUBSTR() function would work like below -

= SUBSTR(productID, 10-3, 4)
= SUBSTR(productID, 7, 4)

Example 2 : Handle missing values while extracting

Suppose you have multiple product IDs in which some of them are missing.

data example2;
input productID $10.;
cards;
AB123ZX253

AB123ZX254
AB123ZX255
;
run;

When you apply SUBSTR() function in case of missing cases, it returns a note in log 'Invalid second argument'. See the image below

To workaround this problem, we can use SUBSTRN() which handles missing cases while extracting.

data example2;
set example2;
referenceid = substrn(productID,length(productID)-3,4);
run;

Example 3 : Get last N digits from a numeric variable

Suppose product ID variable is numeric.

data example3;
input productID;
cards;
12345253

12354234
12354235
;
run;

The SUBSTR() / SUBSTRN() function works only for character variables. In order to make it run for numeric variables, we first need to convert numeric variables to character variables with PUT() function.

data example3;
set example3;
x = put(productID, 10.);
referenceid = input(substrn(x,length(x)-3,4),8.);
drop x;
proc print noobs;
run;

Since SUBSTRN() returns character variable, we need to convert it to numeric with INPUT() function.

Another Method

data example3;
set example3;
referenceid = input(substrn(productID,INT(LOG10(productID))+1-3,4),8.);
proc print noobs;
run;

How it works

1. LOG10(1021) returns 3.009
2. INT(LOG10(1021)) makes it 3
3. Adding 1 to step 2 makes it 4, which is the result of the number of digits in 1021

In this process, we first calculate the logarithm base 10 of the number 1021, which gives us a result of 3.009. Then, by using the INT function, we extract the integer part of the logarithm, resulting in 3. Finally, by adding 1 to the integer part, we determine that the number 1021 has 4 digits.

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About Author:

Deepanshu founded ListenData with a simple objective - Make analytics easy to understand and follow. He has over 10 years of experience in data science. During his tenure, he worked with global clients in various domains like Banking, Insurance, Private Equity, Telecom and HR.

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