Use the READ statement with the VAR clause to read variables from the current SAS data set into column vectors. Each variable in the VAR clause becomes a column vector with the same name as the variable in the SAS data set. The number of rows is equal to the number of observations that are processed, depending on the range specification and the WHERE clause. For example, to read the numeric variables Age, Height, and Weight for all observations in the Sashelp.Class data set, use the following statements:

proc iml;
use Sashelp.Class;
read all var {Age Height Weight};
close Sashelp.Class;

Now use the SHOW NAMES statement to display all the matrices in the current SAS/IML session:

show names;

 SYMBOL   ROWS   COLS TYPE   SIZE                                               
 ------ ------ ------ ---- ------                                               
 Age        19      1 num       8                                               
 Height     19      1 num       8                                               
 Weight     19      1 num       8                                               
  Number of symbols = 5  (includes those without values)                        
                                                                                

Figure 7.11 shows that the READ statement created three numeric vectors: Age, Height, and Weight.

Notice, however, that Figure 7.11 tells you that there are five symbols. The USE statement creates SAS/IML symbols for Name and Sex, but these variables were never read and so the symbols were not assigned values. (You can use the SHOW ALLNAMES statement to see the unassigned symbols.) If the data set contains many variables, it can be more efficient to subset the data set by using the VAR clause in the USE statement. For example, the following statements create the same vectors but do not create symbols for the unread variables:

use Sashelp.Class var {Age Height Weight};
read all;
close Sashelp.Class;