Compare current to previous entry (paradata)

[Shmuel · Accepted solution]

Next is my final tested code.

I have added a test line for landing entry without exit.

Results fits your posted output.

data have;
   length name $6 activity $20 screen $8 value $8;
   infile cards;
   input name $ activity $ screen $ valuex $ ;
   value_time = 0; /* flag */
   if strip(valuex) in ("1" "2") 
      then value = input(strip(valuex),1.);
      else do;
           value = input(valuex,hhmmss.); 
           value_time = 1;
      end;
   timestamp = _N_; /* dummy variable to save original order */
cards;
Mary Home_test_entry Home 2
Mary Home_test_exit  Home 2
Mary Landing_test_entry Landing 1
Mary Landing_test_exit  Landing 2
Mary Login_test_entry Login 1
Mary Login_test_entry Login 2
Mary Login_test_exit Login 1
Mary Login_test_exit Login 2
Mary Login_test_time Login 08:09:12
Mary Candy_test_entry Candy 2
Mary Candy_test_exit Candy 2
Tom Home_test_entry Home 2
Tom Home_test_exit  Home 1
Mary Landing_test_entry Landing 2
Mary Landing_test_exit  Landing 1
Xxxx Landing_test_entry Landing 1
;
run;

proc sort data=have; by name timestamp; run;  
data temp;
 set have;
  by name;  
     length switch $15;
     retain pre_activity pre_value;           
     pre_activity= lag(activity);
     pre_value = lag(value);
     pre_screen = lag(screen);
     drop pre_activity pre_value pre_screen ;
     
     if first.name then do;
        pre_activity = "";
        pre_value = "";
        pre_screen = "";
     end;
     
     if screen = "Landing" then do;
        if activity = "Landing_test_exit" then do;
           if value ne pre_value then do;
              if value=2 
                 then switch = "One-Two";
                 else switch = "Two-One";
           end;
        /* else treat while value = pre_value ??? */
       end;
     end;
	 
	 if screen ne "Landing" and 
        screen = pre_screen then do;
        if value_time = 1
           then switch = "Switch_time"; else
        if value = pre_value 
		   then switch = "No";
           else switch = "Switch_within";
end;
        
run;  

proc sort data=temp; 
  by name descending timestamp; 
run;  

data want;
 set temp;
  by name; 
     length pre_switch $15;
     retain pre_activity pre_value;           
     pre_activity= lag(activity);
     pre_value = lag(value);
     pre_screen = lag(screen);
	 pre_switch = lag(switch);
     drop pre_activity pre_value pre_screen pre_switch;
    
     if first.name then do;
        pre_activity = "";
        pre_value = "";
        pre_screen = "";
     end;
     
     if screen = "Landing" then do;
        if activity = "Landing_test_entry" then do;
           if value ne pre_value then do;
              if value=1 then switch = "One-Two";
              else switch = "Two-One";
           end;
        /* else treat while value = pre_value ??? */ 
       end;
     end;
    
	if screen ne "Landing" and
       /*screen ne pre_screen and*/
       switch = " " 
    then switch = pre_switch;    
run;  
proc sort data=want; by name timestamp; run;  

[lydiawawa]

Thank you Shmuel, I will be able to check the code on Monday, currently, have no access to the data.