Step-by-Step Programming with Base SAS 9.4, Second Edition, 2nd Edition

Figure 19.7 Program Data Vector After Reading from Each Data Set

Abbott, Jennifer .

Abbott, Jennifer Hitchcock-Tyler, Erin .

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4. After processing the first observation from the last data set and executing any other

statements in the DATA step, SAS writes the contents of the program data vector to

the new data set. If the DATA step attempts to read past the end of a data set, then the

values of all variables from that data set in the program data vector are set to

missing.

This behavior has two important consequences:

• If a variable exists in more than one data set, then the value from the last data set

SAS reads is the value that goes into the new data set, even if that value is

missing. If you want to keep all the values for like-named variables from

different data sets, then you must rename one or more of the variables with the

RENAME= data set option so that each variable has a unique name.

• After SAS processes all observations in a data set, the program data vector and

all subsequent observations in the new data set have missing values for the

variables unique to that data set. So, as the next figure shows, the program data

vector for the last observation in the new data set contains missing values for all

variables except Name2.

Figure 19.8 Program Data Vector for the Last Observation

 Wittich, Stefan .

5. SAS continues to merge observations until it has copied all observations from all

data sets.

Match-Merging

Merging with a BY Statement

Merging with a BY statement enables you to match observations according to the values

of the BY variables that you specify. Before you can perform a match-merge, all data

sets must be sorted by the variables that you want to use for the merge.

In order to understand match-merging, you must understand three key concepts:

296 Chapter 19 • Merging SAS Data Sets

BY variable

specifies a variable that is named in a BY statement.

BY value

specifies the value of a BY variable.

BY group

specifies the set of all observations with the same value for the BY variable (if there

is only one BY variable). If you use more than one variable in a BY statement, then a

BY group is the set of observations with a unique combination of values for those

variables. In discussions of match-merging, BY groups commonly span more than

one data set.

Input SAS Data Set for Examples

The director of a small repertory theater company, the Little Theater, maintains company

records in two SAS data sets, COMPANY and FINANCE.

Table 19.1 Variables in the COMPANY and FINANCE Data Sets

Data Set Variable Description

COMPANY Name player's name

Age player's age

Gender player's gender

FINANCE Name player's name

IdNumber player's employee ID number

Salary player's annual salary

The following program creates, sorts, and displays the COMPANY and FINANCE data

sets:

data company;

input Name $ 1-25 Age 27-28 Gender $ 30;

datalines;

Vincent, Martina 34 F

Phillipon, Marie-Odile 28 F

Gunter, Thomas 27 M

Harbinger, Nicholas 36 M

Benito, Gisela 32 F

Rudelich, Herbert 39 M

Sirignano, Emily 12 F

Morrison, Michael 32 M

;

run;

proc sort data=company;

by Name;

run;

Match-Merging 297

data finance;

input IdNumber $ 1-11 Name $ 13-37 Salary;

datalines;

074-53-9892 Vincent, Martina 35000

776-84-5391 Phillipon, Marie-Odile 29750

929-75-0218 Gunter, Thomas 27500

446-93-2122 Harbinger, Nicholas 33900

228-88-9649 Benito, Gisela 28000

029-46-9261 Rudelich, Herbert 35000

442-21-8075 Sirignano, Emily 5000

;

run;

proc sort data=finance;

by Name;

run;

proc print data=company;

title 'Little Theater Company Roster';

run;

proc print data=finance;

title 'Little Theater Employee Information';

run;

The following output displays the COMPANY and FINANCE data sets. Notice that the

FINANCE data set does not contain an observation for Michael Morrison:

Figure 19.9 The COMPANY Data Set

298 Chapter 19 • Merging SAS Data Sets

Figure 19.10 The FINANCE Data Set

The Program

To avoid having to maintain two separate data sets, the director wants to merge the

records for each player from both data sets into a new data set that contains all of the

variables. The variable that is common to both data sets is Name. Therefore, Name is the

appropriate BY variable.

The data sets are already sorted by Name, so no further sorting is required. The

following program merges them by Name:

data employee_info;

merge company finance;

by name;

run;

proc print data=employee_info;

title 'Little Theater Employee Information';

title2 '(including personal and financial information)';

run;

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