Understanding the SUM Statement and Accumulation

This script compares three techniques to calculate a running total of the 'age' variable from the sashelp.class table. It demonstrates the equivalence and nuances between the RETAIN statement combined with a simple addition, the SAS^© sum statement (variable+expression), and the use of the SUM function with RETAIN.

Data Analysis

Type : SASHELP

The data comes from the standard SASHELP.CLASS example table.

1 Code Block

DATA STEP Data

Explanation :
Using the RETAIN statement to preserve the value of 'totage' from one observation to the next, initialized to 0, and manually adding the age.

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1	DATA totalage;
2	SET sashelp.class;
3	retain totage 0;
4	totage = totage+age;
5	RUN;

2 Code Block

DATA STEP Data

Explanation :
Using the Sum Statement 'variable+expression'. This syntax automatically implies RETAIN and handles missing values as zeros for accumulation.

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1	DATA totalage;
2	SET sashelp.class;
3	totage+age;
4	RUN;

3 Code Block

DATA STEP Data

Explanation :
Using the SUM function with explicit RETAIN. The SUM function ignores missing values, unlike the simple '+' operator used in the first example.

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1	DATA totalage;
2	SET sashelp.class;
3	retain totage 0;
4	totage = sum(totage,age);
5	RUN;

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