SAS: Dynamically Setting a Variable Name

Question

In this block of SAS data step code I am setting a Table from an SQL query called TEST_Table. This table contains multiple columns including a larger section of columns titled PREFIX_1 to PREFIX_20. Each column starts with PREFIX_ and then an incrementing number from 1 to 20.

What I would like to do is iteratively cycle through each column and analyze the value of that column.

Below is an example of what I am trying to go for. As you can see I would like to create a variable that increases on each iteration and then I use that count value as a part of the variable name I am checking.

data TEST_Data;
  set TEST_Table;
  retain changing_number;
  
  changing_number=1;
  do while(changing_number<=20);    
    if PREFIX_changing_number='BAD_IDENTIFIER' then do;
      PREFIX_changing_number='This is a bad part';
    end;
  end;  

run;

How would be the best way to do this in SAS? I know I can do it by simply checking each value individually from 1 to 20.

if PREFIX_1 = 'BAD_IDENTIFIER' then do;
  PREFIX_1 = 'This is a bad part';
end;
if PREFIX_2 = ...

But that would be really obnoxious as later I will be doing the same thing with a set of over 40 columns.

Ideas?

SOLUTION

data TEST_Data;
    set TEST_Table;
    
    array SC $ SC1-SC20;
    
    do i=1 to dim(SC);    
      if SC{i}='xxx' then do;
         SC{i}="bad part";
      end;   
    end;  
run;

Thank you for suggesting Arrays :)

You can remove several parts of that with no difference. The {*} is unneeded if you specify the variables explicitly. The i=1; does absolutely nothing. I recommend highly using dim(SC) rather than 20 as it makes your code easier to maintain as well. — Joe
– Joe, Commented Nov 15, 2012 at 22:18

Joe · Accepted Answer · 2012-11-15 21:45:52Z

1

You need to look up Array processing in SAS. Simply put, you can do something like this:

data TEST_Data;
  set TEST_Table;
  *retain changing_number; Remove this - even in your code it does nothing useful;
  array prefixes prefix:; *one of a number of ways to do this;
  changing_number=1;
  do while(changing_number<=20);    
    if prefixes[changing_number]='BAD_IDENTIFIER' then do;
       prefixes[changing_number]='This is a bad part';
    end;
  end;  

run;

A slightly better loop is:

do changing_number = 1 to dim(prefixes);
... loop ...
end;

As that's all in one step, and it is flexible with the number of array elements (dim = number of elements in the array).

edited Nov 15, 2012 at 21:45

answered Nov 15, 2012 at 21:36

Joe

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