/******************version 1***************/
proc iml;
use duality;
read all var {index} into x;
read all var {year} into y;
z=j(nrow(x),2,.);
m=1;
 do i=2 to nrow(y);
    if x[i,1]=x[i-1,1] & y[i,1]-y[i-1,1]=1 then do;
      z[i,1]=m+1;
      m=m+1;
     end;
    else do;
    m=1;
    end;

  if z[i,1]>=5 then do;   /* at least 5 years consecutively, can be modified*/
    do j=0 to z[i,1]-1;
     z[i-j,2]=1;
    end;
 end;
end;

cname={'consecutive' 'filter'} ;
create out from z[colname=cname];
append from z;
quit;

data new;
merge duality out;
if filter=1;  /* filter*/
run;





/*******version 2************/

proc iml;
use duality;
read all var {index} into x;
read all var {year} into y;
z=j(nrow(x),2,.);
m=1;
 do i=2 to nrow(y);
    if x[i,1]=x[i-1,1] & y[i,1]-y[i-1,1]=1 then do;
      z[i,1]=m+1;
      m=m+1;
     end;
    else do;
    m=1;
    end;

    j=i;
    do while (z[j,1]^=.);
     z[j,2]=z[i,1];
     j=j-1;
     if z[j,1]=.  then z[j,2]=z[j+1,2];
 end;
 end;
cname={'consecutive' 'filter'} ;
create out from z[colname=cname];
append from z;
quit;

data new;
merge duality out;
if filter>=5; /*at least 5 year*/
run;