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An Introductory Interactive Session

Here is a simple introductory session that uses SAS/IML software to estimate the square root of a number, accurate to three decimal places. In this session, you define a function module named APPROX to perform the calculations and return the approximation. You then call APPROX to estimate the square root of several numbers given in a matrix literal (enclosed in braces), and you print the results.

Throughout the session, the right angle brackets (>) indicate statements that you submit; responses from PROC IML follow.

  
    >   proc iml;                            /* begin IML session */ 
  
        IML Ready 
  
    >   start approx(x);                          /* begin module */ 
    >      y=1;                                   /* initialize y */ 
    >      do until(w<1e-3);                     /* begin DO loop */ 
    >         z=y;                                     /* set z=y */ 
    >         y=.5#(z+x/z);               /* estimate square root */ 
    >         w=abs(y-z);           /* compute change in estimate */ 
    >      end;                                    /* end DO loop */ 
    >      return(y);                     /* return approximation */ 
    >   finish approx;                              /* end module */ 
  
        NOTE: Module APPROX defined. 
  
    >   t=approx({3,5,7,9});             /* call function APPROX  */ 
    >   print t;                                  /* print matrix */ 
  
                                           T 
                                   1.7320508 
                                    2.236068 
                                   2.6457513 
                                           3 
  
    >  quit; 
  
       Exiting IML