show all values in categorical variable - sas

Question

The google search has been difficult for this. I have two categorical variables, age and months, with 7 levels each. for a few levels, say age =7 and month = 7 there is no value and when I use proc sql the intersections that do not have entries do not show, eg:
age month value
1 1 4
2 1 12
3 1 5
....
7 1 6
...
1 7 8
....
5 7 44
6 7 5
THIS LINE DOESNT SHOW
what i want
age month value
1 1 4
2 1 12
3 1 5
....
7 1 6
...
1 7 8
....
5 7 44
6 7 5
7 7 0
this happens a few times in the data, where tha last groups dont have value so they dont show, but I'd like them to for later purposes

Answer 1

You have a few options available, both seem to work on the premise of creating the master data and then merging it in.
Another is to use a PRELOADFMT and FORMATs or CLASSDATA option.
And the last - but possibly the easiest, if you have all months in the data set and all ages, then use the SPARSE option within PROC FREQ. It creates all possible combinations.
proc freq data=have;
table age*month /out = want SPARSE;
weight value;
run;

Answer 2

First some sample data:
data test;
do age=1 to 7;
do month=1 to 12;
value = ceil(10*ranuni(1));
if ranuni(1) < .9 then
output;
end;
end;
run;
This leaves a few holes, notably, (1,1).
I would use a series of SQL statements to get the levels, cross join those, and then left join the values on, doing a coalesce to put 0 when missing.
proc sql;
create table ages as
select distinct age from test;
create table months as
select distinct month from test;
create table want as
select a.age,
a.month,
coalesce(b.value,0) as value
from (
select age, month from ages, months
) as a
left join
test as b
on a.age = b.age
and a.month = b.month;
quit;

Answer 3

The group independent crossing of the classification variables requires a distinct selection of each level variable be crossed joined with the others -- this forms a hull that can be left joined to the original data. For the case of age*month having more than one item you need to determine if you want
rows with repeated age and month and original value
rows with distinct age and month with either
aggregate function to summarize the values, or
an indication of too many values
data have;
input age month value;
datalines;
1 1 4
2 1 12
3 1 5
7 1 6
1 7 8
5 7 44
6 7 5
8 8 1
8 8 11
run;
proc sql;
create table want1(label="Original class combos including duplicates and zeros for absent cross joins")
as
select
allAges.age
, allMonths.month
, coalesce(have.value,0) as value
from
(select distinct age from have) as allAges
cross join
(select distinct month from have) as allMonths
left join
have
on
have.age = allAges.age and have.month = allMonths.month
order by
allMonths.month, allAges.age
;
quit;
And a slight variation that marks duplicated class crossings
proc format;
value S_V_V .t = 'Too many source values'; /* single valued value */
quit;
proc sql;
create table want2(label="Distinct class combos allowing only one contributor to value, or defaulting to zero when none")
as
select distinct
allAges.age
, allMonths.month
, case
when count(*) = 1 then coalesce(have.value,0)
else .t
end as value format=S_V_V.
, count(*) as dup_check
from
(select distinct age from have) as allAges
cross join
(select distinct month from have) as allMonths
left join
have
on
have.age = allAges.age and have.month = allMonths.month
group by
allMonths.month, allAges.age
order by
allMonths.month, allAges.age
;
quit;
This type of processing can also be done in Proc TABULATE using the CLASSDATA= option.