Used for: Names the SAS data set and creates the dataset.
In a Data step the following can be performed.
- defining
the variables
- read
input files
- assign
values to the variables,
- creating
new variables,
- merging
two or more data sets
- formatting
and labeling variables
- assignment
of missing values.
If a variable
is used in a SAS program but not initialized then SAS automatically assigns a
missing value to it.
Numeric missing
values are represented by a single period (.). Character missing values are
represented by a single
blank enclosed
in quotes (' ').
Syntax:
DATA
<SOMENAME>;
The DATA step
starts with the DATA statement.
The data set
name should be 1-32 characters and must begin with a letter or underscore.
Any text within
<> represents optional material or a user defined name or value.
Example:
DATA EMPDAT;
The following
SAS statements can be used in a DATA step.
2.1 INFILE AND
INPUT STATEMENT
Used for:
INFILE is used to read external files (such as mainframe file, text files,
comma delimited files etc).
INPUT is used
to define names and order of variables for the SAS dataset.
Syntax:
INFILE
file-specification <options>;
INPUT variable
variable_type column(s);
Example1:
DATA EMPFL;
INFILE 'c:\emp\external\emp1.dat';
INPUT
@001 EMPNO $CHAR6.
@007 NAME $CHAR15.
@022 AGE 3.;
RUN;
In this example
the external file “emp1.dat” which is stored in the location “c:\emp\external”
will be read and copied into SAS file
EMPFL. Three variables EMPNO, NAME and AGE will be read.
2.2 SET
STATEMENT
Used for: Reads
one or more existing SAS datasets
Syntax:
SET <SAS dataset
name> <(OBS=n)>;
Where “n” is
the number of observations you want to read from the file.
Example1:
Copies first
100 records of OLDFILE1 to NEWFILE.
DATA NEWFILE;
SET OLDFILE1 (OBS=100);
RUN;
Example2:
Concatenate two
datasets.
Input SAS
datasets:
DATA COMMON;
SET NWEST SWEST;
RUN;
2.3 IF/THEN;
ELSE; STATEMENT
Used for: Used
for conditional checking. Used in a data step.
Syntax:
IF expression THEN
statement;
<ELSE
statement;>
Example:
IF LANG='Spanish' or
LANG='French' THEN
NEWLANG='NotEngl';
ELSE
NEWLANG='English';
In this example
‘Spanish’ is a character constant.
Example 2:
IF status=‘M' AND
type=1 THEN count=count+1;
2.4 SUBSETTING
“IF” STATEMENT
Used for: To
subset, or take a portion of the data set
Syntax:
IF expression;
Where
expression is any SAS expression.
Example:
DATA FORGNER;
IF LANG= ‘ENGLISH’ AND TAX >= 20000;
RUN;
In the above
example the subsetting IF statements will select all observations where LANG
equals ‘ENGLISH’ and
where TAX
greater than and equal to 20000.
Notice that
values for character variables must be enclosed in quotes and values must match
exactly including case.
2.5 LIBNAME
STATEMENT
Used for:
Associates a libref with a SAS library. It’s kind of location pointer.
This is
generally used when we want to save the SAS dataset in a permanent location.
When a libref is not
associated with
SAS dataset, SAS assumes it is created or read from SAS work area which is
temporary in nature.
Syntax:
LIBNAME libref
<engine>'('SAS-data-library-1' <,..'SAS-data-library-n'> ) ';
Example:
In windows –
LIBNAME EMPLIB1
‘C:\data\SAS\EMPDATA’;
The path
‘C:\data\SAS\EMPDATA’ will be assigned to libref EMPLIB1. Say there is a SAS
dataset EMPDAT in that
library, it can be
access as,
DATA EMPFILE1;
SET EMPLIB1.EMPDAT;
RUN;
In Unix –
LIBNAME CLAIM
‘\data\CL\CLAIM\INPUT’;
DATA
CLAIM.LOSS_HISTORY;
SET LOSS_TEMP;
RUN;
In this example
the temporary file LOSS_TEMP will be stored in a permanent location
‘\data\CL\CLAIM\INPUT’
with a new name
LOSS_HISTORY.
2.6 MERGE
STATEMENT
Used for: Joins
corresponding observations from two or more SAS data sets.
Syntax:
DATA new-sasdataset;
MERGE SAS dataset name-1 SAS dataset name-2
... SAS dataset name-n;
BY var1 var2 varm;
RUN;
Input data sets
must be sorted by the same BY variables before you can merge them.
Example:
Merge the two
files SURVY and NAMES by the variable NAME.
DATA NEW;
MERGE NAMES
SURVY;
BY NAME;
RUN;
