READ Statement

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Language Reference

READ Statement

reads observations from a data set

READ <range> <VAR operand> <WHERE(expression)>

<INTO name <[ROWNAME=row-name

COLNAME=column-name]>> ;

The inputs to the READ function are as follows:

range: specifies a range of observations.
operand: selects a set of variables.
expression: is evaluated for being true or false.
name: is the name of the target matrix.
row-name: is a character matrix or quoted literal giving descriptive row labels.
column-name: is a character matrix or quoted literal giving descriptive column labels.

The clauses and options are explained below.

Use the READ statement to read variables or records from the current SAS data set into column matrices of the VAR clause or into the single matrix of the INTO clause. When the INTO clause is used, each variable in the VAR clause becomes a column of the target matrix, and all variables in the VAR clause must be of the same type. If you specify no VAR clause, the default variables for the INTO clause are all numeric variables. Read all character variables into a target matrix by using VAR _CHAR_.

You can specify a range of observations with a keyword or by record number using the POINT option. You can use any of the following keywords to specify a range:

ALL

all observations

CURRENT

the current observation

NEXT <number>

the next observation or the next number of observations

AFTER

all observations after the current one

POINT operand

observations specified by number, where operand can be one of the following:

Operand	Example
a single record number	`point 5`
a literal giving several	`point {2 5 10}`
record numbers
the name of a matrix	`point p`
containing record numbers
an expression in parentheses	`point (p+1)`

If the current data set has an index in use, the POINT option is invalid.

You can specify a set of variables to use with the VAR clause. The operand in the VAR clause can be one of the following:

a literal containing variable names
the name of a matrix containing variable names
an expression in parentheses yielding variable names
one of keywords described below:

_ALL_
for all variables
_CHAR_
for all character variables

_NUM_
for all numeric variables.

Below are examples showing each possible way you can use the VAR clause:

   var {time1 time5 time9}; /* a literal giving the variables */
   var time;                /* a matrix containing the names  */
   var('time1':'time9');    /* an expression                  */
   var _all_;               /* a keyword                      */

The WHERE clause conditionally selects observations, within the range specification, according to conditions given in the clause. The general form of the WHERE clause is

WHERE( variable comparison-op operand)

In the statement above,

variable

is a variable in the SAS data set.

comparison-op

is one of the following comparison operators:

<: less than
<=: less than or equal to
=: equal to
>: greater than
>=: greater than or equal to
=: not equal to
?: contains a given string
?: does not contain a given string
=:: begins with a given string
=*: sounds like or is spelled similar to a given string

operand

is a literal value, a matrix name, or an expression in parentheses.

WHERE comparison arguments can be matrices. For the following operators, the WHERE clause succeeds if all the elements in the matrix satisfy the condition:

= ? < <= > >=

For the following operators, the WHERE clause succeeds if any of the elements in the matrix satisfy the condition:

= ? =: =*

Logical expressions can be specified within the WHERE clause using the AND (&) and OR (|) operators. The general form is

clause&clause (for an AND clause)

clause|clause (for an OR clause)

where clause can be a comparison, a parenthesized clause, or a logical expression clause that is evaluated using operator precedence.

Note: The expression on the left-hand side refers to values of the data set variables, and the expression on the right-hand side refers to matrix values.

You can specify ROWNAME= and COLNAME= matrices as part of the INTO clause. The COLNAME= matrix specifies the name of a new character matrix to be created. This COLNAME= matrix is created in addition to the target matrix of the INTO clause and contains variable names from the input data set corresponding to columns of the target matrix. The COLNAME= matrix has dimension 1 ×nvar, where nvar is the number of variables contributing to the target matrix.

The ROWNAME= option specifies the name of a character variable in the input data set. The values of this variable are put in a character matrix with the same name as the variable. This matrix has the dimension nobs×1, where nobs is the number of observations in the range of the READ statement. The range, VAR, WHERE, and INTO clauses are all optional and can be specified in any order.

Row names created via a READ statement are permanently associated with the INTO matrix. You do not need to use a MATTRIB statement to get this association.

For example, to read all observations from the data set variables NAME and AGE, use a READ statement with the VAR clause and the keyword ALL for the range operand. This creates two IML variables with the same names as the data set variables.

   read all var{name age};

To read all variables for the 23rd observation only, use the statement

   read point 23;

To read the data set variables NAME and ADDR for all observations with a STATE value of NJ, use the statement

   read all var{name addr} where(state="NJ");

See Chapter 6, "Working with SAS Data Sets," for further information.

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	clause&clause	(for an AND clause)
	clause\|clause	(for an OR clause)