/************************************************
*   Making spin-plot varing the coefficient     *
*   for variable x1x2 only (the interaction)    *
* In the process, only one parameter is varing, *
* that is the bx1x2 term. The corresponding     *
* fixed string length parameter is called bf.   *
* You can use it in your title statement.       *
************************************************/ 
%macro sp_plotbx1x2(outfile="c:\sp_plotbx1x2.gif", data=_spinplt ,
                    x1lo=-10, x1hi=10, x1by=1, x2lo=-10, x2hi=10, x2by=1,
			        cons=0, bx1=0, bx2=0, bx1x2=0, bx1x1=0, bx2x2=0, bx1x1x2=0, bx1x2x2=0,
                    title=Spin Plot, title2=' ',
                    plot=, gopt=, angle=100, slen=6, bx1x2_lo=-1, bx1x2_hi=1, bx1x2_by=.25, 
                    cmd=plot); 

  * reset graph settings ;
  goptions reset=all;

  filename out clear ;
  filename out &outfile ;

  * assign graphics options for the animation; 
  goptions gsfname=out dev=gifanim gcopies=0 iteration=0 delay=50 &gopt;

  %let bx1x2_lo_ = %sysevalf(&bx1x2_lo*100);
  %let bx1x2_hi_ = %sysevalf(&bx1x2_hi*100);
  %let bx1x2_by_ = %sysevalf(&bx1x2_by*100);

  * make graph going forward from bx1x2lo to bx1x2hi ;
  %do bx1x2_ = &bx1x2_lo_ %to &bx1x2_hi_ %by &bx1x2_by_ ;
    %let bx1x2 = %sysevalf(&bx1x2_ / 100);
 
    %if &bx1x2_ =  &bx1x2_lo_ %then %do; goptions gsfmode=replace; %end;
    %if &bx1x2_ >  &bx1x2_lo_ %then %do; goptions gsfmode=append; %end;

    %local bstring;
    %fixlen(&bx1x2, &slen);
    %let title =&title;
    %let title2=%str(y=&cons+)%str(&bx1)%str(*x1+&bx2*x2&bstring*x1*x2+&bx1x1*x1x1+&bx2x2*x2x2+&bx1x1x2*x1x1x2+&bx1x2x2*x1x2x2);

   
    %sp_plot(angle=&angle, data=&data ,
             x1lo=&x1lo, x1hi=&x1hi, x1by=&x1by, x2lo=&x2lo, x2hi=&x2hi, x2by=&x2by,
	         cons=&cons, bx1=&bx1, bx2=&bx2, bx1x2=&bx1x2,
             bx1x1=&bx1x1, bx2x2=&bx2x2, bx1x1x2=&bx1x1x2, bx1x2x2=&bx1x2x2, 
             title=&title, title2=&title2, plot=&plot, gopt=&gopt, cmd=&cmd, reset=no ); 
  %end;

  * make graph going backward from bx1x2hi to bx1x2lo ;
  %do bx1x2_ = &bx1x2_hi_ %to &bx1x2_lo_ %by -&bx1x2_by_ ;
    %let bx1x2 = %sysevalf(&bx1x2_ / 100);
 
    %if &bx1x2_ >  &bx1x2_hi_ %then %do; goptions gsfmode=append; %end;  
    %if &bx1x2_ <= &bx1x2_lo_ %then %do; goptions gepilog='3B'x; %end;

   %local bstring;
  %fixlen(&bx1x2, &slen);
  %let title =&title;
  %let title2=%str(y=&cons+)%str(&bx1)%str(*x1+&bx2*x2&bstring*x1*x2+&bx1x1*x1x1+&bx2x2*x2x2+&bx1x1x2*x1x1x2+&bx1x2x2*x1x2x2);
  

    %sp_plot(angle=&angle, data=&data,
             x1lo=&x1lo, x1hi=&x1hi, x1by=&x1by, x2lo=&x2lo, x2hi=&x2hi, x2by=&x2by,
	         cons=&cons, bx1=&bx1, bx2=&bx2, bx1x2=&bx1x2,
             bx1x1=&bx1x1, bx2x2=&bx2x2, bx1x1x2=&bx1x1x2, bx1x2x2=&bx1x2x2, 
             title=&title, title2=&title2, plot=&plot,gopt=&gopt,cmd=&cmd, reset=no); 
  %end;

  filename out clear ;
  goptions reset = all;
  title ;
%mend sp_plotbx1x2;