Ornstein-Unlenbeck in Maple

gistfile1.txt

 restart;
 with(Statistics):
 STDNORM:=proc( ) local ij,U1,U2,S,B,X1;global i,X2;
       if type(i,boolean)then
       if (i) then
           i:=not(i);X2;
       else
           for ij from 1 to infinity do  
              U1:=evalf(2.0*rand()/10^12)-1.0;
              U2:=evalf(2.0*rand()/10^12)-1.0;
              S:=U1*U1+U2*U2;
              if(S=1.0 or S<=0.0) then next end if;
              B:=sqrt(-2.0*ln(S)/S);
              X1:=B*U1;
              X2:=B*U2;
              break;
           end do;
           i:=not(i);X1;
       end if;
       else ERROR("i should be boolean") end if;
 end proc:
 
 meanreverting:=proc(T,n,alpha,m,nu,y0) local h,P,j,z,a,b,d,A,Y;
   global i,X2;
   i:=false;
   h:=T/n;
   Y:=y0;
   P[0]:=[0,evalf(y0)];
   a:=evalf(exp(-alpha*h));
   b:=sqrt(1-a^2);
   d:=m*(1-a);
   for j from 1 to n do;
      z:=STDNORM();
      Y:=d+Y*a+nu*b*z;
      P[j]:=[evalf(j*h),Y];
   end do;
   seq(P[j],j=0..n);
 end proc:
 
 y0:= 0.02673189: m:= 0.0051: nu:= 0.51936: N:= 12: M:= 1000: T:= 1: h := T/N:alpha:=20:  
 randomize():
 SPr := seq([meanreverting(T,N,alpha,m,nu,y0)], i = 1 .. M):
 for k to N do:
   RIU[k] := Mean([seq(SPr[i][k][2], i = 1 .. M)]):
 end do:
 RIU_plot:=seq(RIU[k],k=1..12);
 PLOT(CURVES(SPr),TITLE("Прогноз темпов роста аудитории российского интернета"));
 #PLOT(CURVES(RIU_plot),TITLE("Прогноз темпов роста аудитории российского интернета"));


  RIU_plot := 0.02673189000, 0.002775788100, 0.0007051991596,

        0.01460316795, -0.001395036910, 0.01100092534, 0.02954795427,

        0.01744122578, 0.01662275555, 0.03567445478, -0.004317302288,

        0.05583135921