Date:         Mon, 3 May 2010 10:15:32 -0400
Reply-To:     "P. Cristian Gugiu" <crisgugiu@YAHOO.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "P. Cristian Gugiu" <crisgugiu@YAHOO.COM>
Subject:      Help with macro variables

Hi all. I wrote code for calculating a double integral using the Trapezoid
Rule. However, I need to pass a value out of the macro and keep running
into problems. Can someone tell me how I can assign the value for the
variable "Volume" to a macro variable that I can use outside of the macro.

Thanks,
Cristian


%Let Pi=3.1415926535897932384626433832795;
%Macro Trapezoid(minX=,maxX=,minY=,maxY=,func=,lbl=);
%Global mu;
data _NULL_;
 delta=.1;
 dx=delta; dy=delta;
 sum=0;
 do x=&minX to &maxX by dx;
  if round(x,dx) eq &minX OR round(x,dx) eq &maxX then mX=1;
   else mX=2;
  do y=&minY to &maxY by dy;
   if round(y,dy) eq &minY OR round(y,dy) eq &maxY
then mY=1;
    else mY=2;
   sum=sum + mX*mY*(&func);
  end;
 end;
 Volume=round(0.25*dx*dy*sum,.00000001);
 %let mu= input(Volume,best4.);
 put "&lbl=" Volume;
 %put &mu;
run;quit;
%Mend Trapezoid;
%let mu1=29.9924961;   /* Mean of X     */
%let var1=23.2736469;  /* Variance of X */
%let mu2=9.99274913;   /* Mean of Y     */
%let var2=0.24619424;  /* Variance of Y */
%let rho=0.75046;    /* Correlation b/w X and Y */

%let g_xy=(sqrt(abs(x*y))); /* Function      */
%let pdf = (1/(2*&Pi*sqrt(&var1*&var2*(1-&rho**2))))*exp(-(1/(2*(1-
&rho**2)))*(((x-&mu1)**2)/&var1 + ((y-&mu2)**2)/&var2 - 2*&rho*(x-&mu1)*(y-
&mu2)/sqrt(&var1*&var2)));

/* Estimate mean of E(Z)=E[g(X,Y)] */
%let function=&g_xy * &pdf;
%Trapezoid(minX=-100,maxX=100,minY=-100,maxY=100,func=&function,lbl=Mean);