Sas calculation program doesn't run -

i have following data set:

date    jobboardid       sales jan05     3              256     jan05     6              70 jan05     54             90     feb05     32             456 feb05     11             89 feb05     16             876 march05 april05 .  . . jan06     6              678 jan06     54             87 jan06     13             56  feb06     mcdonald       67 feb06     11             281 feb06     16             876 march06 april06 . . . jan07    6               567 jan07    54              76 jan07    34              87 feb07    10              678 feb07    11              765 feb07    16              67 march07    april06 

i trying calculate 12 month growth rate sales column when jobboardid column has same value 12 months apart. have following code:

data want; set have; date jobboardid; format till monyy7.; = lag12(date); oldsales = lag12(sales);  if lag12 (jobboardid) eq jobboardid  , intck('month', from, date) eq 12 do;     till = date;     rate =  (sales - oldsales) / oldsales;     output; end; run; 

however keep getting following error message: note: missing values created result of performing operation on missing values.

but when checked dataset, there aren't missing values. what's problem?

note: date column in monyy7. format. jobboardid numeric value , sales.

the note being thrown intck() function. when from=lag12(date) first 12 records have missing value from. , intck('month', from, date) throw note. though intck not used in assignment statement, still throws note because 1 of arguments has missing value. below example. log reports missing values created 12 times, because used lag12.

77   data have; 78     date=1 20; 79       output; 80     end; 81   run;  note: data set work.have has 20 observations , 1 variables.  82   data want; 83     set have; 84     from=lag12(date); 85     if intck('month',from,today())=. put 'missing: ' (_n_ date)(=); 86     else put 'not missing: ' (_n_ date)(=); 87   run;  missing: _n_=1 date=1 missing: _n_=2 date=2 missing: _n_=3 date=3 missing: _n_=4 date=4 missing: _n_=5 date=5 missing: _n_=6 date=6 missing: _n_=7 date=7 missing: _n_=8 date=8 missing: _n_=9 date=9 missing: _n_=10 date=10 missing: _n_=11 date=11 missing: _n_=12 date=12 not missing: _n_=13 date=13 not missing: _n_=14 date=14 not missing: _n_=15 date=15 not missing: _n_=16 date=16 not missing: _n_=17 date=17 not missing: _n_=18 date=18 not missing: _n_=19 date=19 not missing: _n_=20 date=20 note: missing values generated result of performing operation on missing values.       each place given by: (number of times) @ (line):(column).       12 @ 85:6 note: there 20 observations read data set work.have. note: data set work.want has 20 observations , 2 variables. 

one way avoid problem add block (untested):

if lag12 (jobboardid) eq jobboardid , _n_> 12 do;   if intck('month', from, date) eq 12 do;       till = date;       rate =  (sales - oldsales) / oldsales;       output;   end; end;