Examples: Processing BY Groups in the DATA Step

Analyzing BY groups in SAS^© is a powerful feature for selectively processing data. By using the BY statement in a DATA step, you can organize observations into groups based on the values of one or more variables. This facilitates the execution of specific operations (calculations, aggregations, etc.) for each data group, thereby improving code efficiency and clarity. The SORT procedure is generally used before processing BY groups to sort the data according to the BY variables, as this is a fundamental requirement. The OUT= option of PROC SORT allows the creation of a new sorted dataset, although in some examples, the original dataset may be replaced. The document explores use cases with a single BY variable, multiple BY variables, and the GROUPFORMAT option for managing custom formats.

Data Analysis

Type : INTERNAL_CREATION

The examples use data generated via datalines, ensuring their autonomy.

1 Code Block

DATA STEP / PROC SORT Data

Explanation :
This example shows how to group data using a single BY variable, `zipCode`, in a DATA step. The `zip` dataset contains street names, cities, states, and zip codes. Groups are created by specifying the `zipCode` variable in the BY statement. The DATA step arranges zip codes with the same values into groups. The figure shows five BY groups being created.

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1	DATA zip;
2	INPUT zipCode State $ City $ Street $20-29;
3	DATALINES;
4	85730 AZ Tucson Domenic Ln
5	85730 AZ Tucson Gleeson Pl
6	33133 FL Miami Rice St
7	33133 FL Miami Thomas Ave
8	33133 FL Miami Surrey Dr
9	33133 FL Miami Trade Ave
10	33146 FL Miami Nervia St
11	33146 FL Miami Corsica St
12	33801 FL Lakeland French Ave
13	33809 FL Lakeland Egret Dr
14	;
15
16	PROC SORT DATA=zip;
17	BY zipCode;
18	RUN;
19
20	DATA zip;
21	SET zip;
22	BY zipCode;
23	RUN;
24
25	PROC PRINT DATA=zip noobs;
26	title 'BY-Group Uing a Single Variable: ZipCode';
27	RUN;

2 Code Block

DATA STEP / PROC SORT Data

Explanation :
This example shows the results of processing the `zip` dataset with two BY variables, State and City. The figure shows three BY groups. The dataset is displayed with the BY variables State and City printed on the left for easy reading. The position of BY variables in observations does not affect how values are grouped and ordered.

Observations are organized so that observations for Arizona appear first. Observations within each State value are organized in order of the City value. Each BY group has a unique combination of values for the State and City variables. For example, the BY value of the first BY group is `AZ Tucson`, and the BY value of the second BY group is `FL Lakeland`.

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1	DATA zip;
2	INPUT State $ City $ Street $13-22 ZipCode ;
3	DATALINES;
4	FL Miami Nervia St 33146
5	FL Miami Rice St 33133
6	FL Miami Corsica St 33146
7	FL Miami Thomas Ave 33133
8	FL Miami Surrey Dr 33133
9	FL Miami Trade Ave 33133
10	FL Lakeland French Ave 33801
11	FL Lakeland Egret Dr 33809
12	AZ Tucson Domenic Ln 85730
13	AZ Tucson Gleeson Pl 85730
14	;
15
16
17	PROC SORT DATA=zip;
18	BY State City;
19	RUN;
20
21	DATA zip;
22	SET zip;
23	BY State City;
24	RUN;
25	PROC PRINT DATA=zip noobs;
26	title 'BY Groups with Multiple BY Variables: State City';
27	RUN;

3 Code Block

DATA STEP / PROC FORMAT Data

Explanation :
This example uses the FORMAT procedure, the GROUPFORMAT option, and the FORMAT statement to create and print a simple dataset. The input TEST dataset is sorted by increasing values. The NEWTEST dataset is organized by the formatted values of the Score variable. The example uses the GROUPFORMAT option and the FORMAT statement to create and print a simple dataset.

Key ideas:
- Processing BY groups in the DATA step using the GROUPFORMAT option is the same as processing BY groups with formatted values in SAS procedures. Using the GROUPFORMAT option is useful when defining your own formats to display grouped data.
- Using the GROUPFORMAT option in the DATA step ensures that the BY groups you use to create a dataset match the BY groups in the PROC steps that report grouped and formatted data. GROUPFORMAT also determines how the FIRST.variable and LAST.variable are assigned.

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1	options
2	linesize=80 pagesize=60;
3
4	DATA test;
5	INPUT name $ Score;
6	DATALINES;
7	Jon 1
8	Anthony 3
9	Miguel 3
10	Joseph 4
11	Ian 5
12	Jan 6
13	;
14	PROC FORMAT;
15	value Range 1-2='Low'
16	3-4='Medium'
17	5-6='High';
18	RUN;
19
20	DATA newtest;
21	SET test;
22	BY groupformat Score;
23	FORMAT Score Range.;
24	RUN;
25
26	PROC PRINT DATA=newtest;
27	title 'Score Categories';
28	var Name Score;
29	BY Score;
30	RUN;

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