SAS: Identify Lag and Lead Status by Row

For character variable.

data want;
set have;
by id;
set  have (firstobs =2 keep = index0 rename= (index0= index1))
     have (obs=1 drop = _all_ );
indexlag1 = ifc( first.id, '', lag1(index0));
index1 = ifc( last.id, '', index1);
run;

For numeric variable.

data want;
set have;
by id;
set  have (firstobs =2 keep = index0 rename= (index0= index1))
     have (obs=1 drop = _all_ );
indexlag1 = ifn( first.id, (.), lag1(index0));
index1 = ifn( last.id, (.) , index1);
run;

SAS: Identify Row Level Changes and Tagging

Sort the dataset first and identify the change using lag(var).
The example below shows if the student cumulative credits drops from previous term, the count of degree will increase by 1.

/* identify the row observation that the change took place */
data data2;
set data1;
by sisid term; 
if first.sisid then deg =1;
else if sisid = lag1(sisid) and cumm_cr < lag1(cumm_cr) then deg = 2;
run;
/* tagging the observations associated with the change */
data data3 ;
set data2;
by sisid;
retain temp;
if first.sisid then do; temp = 0; end;
if deg ne . then temp = deg;
else if deg eq . then deg= temp;
run;

Updated to

data data2;
set data1;
by sisid term; 
retain deg;
if first.sisid then deg =1;
else if sisid = lag1(sisid) and cumm_cr < lag1(cumm_cr) then deg = deg +1;
run;