Arrays

A SAS array is a temporary name for a group of variables, so you can process them in a loop instead of writing the same statement ten times. It isn't stored in the data set — the variables are.

Cleaning many columns at once

A survey uses 9 for "no answer" in questions q1–q5:

data survey;
   input id q1-q5;
   array q{5} q1-q5;
   do i = 1 to 5;
      if q{i} = 9 then q{i} = .;
   end;
   answered = n(of q1-q5);
   avg = mean(of q{*});
   format avg 4.2;
   drop i;
   datalines;
1 4 5 9 3 4
2 2 9 9 1 5
;
run;

proc print data=survey noobs;
run;

id    q1    q2    q3    q4    q5    answered     avg

 1     4     5     .     3     4        4       4.00
 2     2     .     .     1     5        3       2.67

• q1-q5 is a variable list: q1 q2 q3 q4 q5.
• array q{5} q1-q5; — q{1} is q1, q{2} is q2, and so on. Braces, brackets, or parentheses all work.
• of q{*} or of q1-q5 passes every element to a function.
• N() counts non-missing values; MEAN() ignores missing values.
• dim(q) returns the number of elements — use do i = 1 to dim(q); so the loop stays right if the array changes.

Wide to long

Arrays with OUTPUT turn one row per person into one row per value:

data long;
   set survey;
   array q{5} q1-q5;
   do question = 1 to 5;
      answer = q{question};
      output;
   end;
   keep id question answer;
run;

proc print data=long(obs=6) noobs;
run;

id    question    answer

 1        1          4
 1        2          5
 1        3          .
 1        4          3
 1        5          4
 2        1          2

PROC TRANSPOSE does the same job; arrays give you more control.

Temporary arrays

_TEMPORARY_ arrays hold values without creating variables — ideal for lookup tables:

data _null_;
   array limits{3} _temporary_ (50 70 90);
   score = 75;
   level = 0;
   do i = 1 to dim(limits);
      if score >= limits{i} then level = i;
   end;
   put score= level=;
run;

score=75 level=2

Character arrays

Add $ and a length for character variables: array names{3} $ 20 name1-name3;. array nums{*} _numeric_; and array chars{*} _character_; cover every numeric or character variable in the step.

Common mistakes

• ERROR: Array subscript out of range — the loop goes past the last element; use dim().
• Mixing types — every element must be numeric or every element must be character.