SDA 3.5 Documentation for CASEStoDDL

NAME

DESCRIPTION

There are many options available to customize the content of a DDL file produced from a CASES instrument. However, there are default options which will usually produce satisfactory results, at least as a starting point. The purpose of this document is to illustrate how to run the procedures in a simple way, taking advantage of the default options.

STEPS OF THE PROCESS

1. Create a list of variables to output
2. Create a list of cases to include in the data file
3. Create the data file by running the CASES ‘output’ program
4. Run the SDA ‘q4toddl’ program
5. Add study-level information to the DDL file
6. Check the DDL file

1. CREATE A LIST OF VARIABLES TO OUTPUT

One way to obtain a list of variables is to run the CASES ‘layout’ program to generate a list of variables. When running the ‘layout’ program, use the ‘-b’ (brief) and the ‘-o’ (only variables) options.

• The ‘-b’ option requests ‘brief’ output, with item names alone, and without other information on each item.

• The ‘-o’ option requests that only items with a defined width be listed. This means that the ‘nodata’ items are omitted.

That list produced by ‘layout’ can then be edited down to the variables that are of substantive interest -- by deleting fills, and various other non-input items.

Save the final list of variables in a file named something like ‘myvars’, for input into the third stage of the process.

2. CREATE A LIST OF CASES TO INCLUDE IN THE DATA FILE

The CASES ‘caselist’ program produces lists of cases, according to criteria that you specify. The precise criteria to use depend on your treatment of completed cases -- whether they have been run through the second-stage cleaning process, for example. Typically, you would specify that the ‘caselist’ program produce a list of all cases that are in one of the following stages: in ‘middle’ or in ‘ready’ or in ‘certified’.

Save that list of cases in a file named something like ‘idlist’, for input into the next stage of the process

3. CREATE THE DATA FILE BY RUNNING THE CASES OUTPUT PROGRAM

For example, if the file ‘myvars’ contains a list of variables for CASES to output, and if the file ‘idlist’ contains a list of the case IDs to be output, you could use the following command:

output -i=myvars -ou=mydata  idlist

• An ASCII data file named ‘mydata’.
• A layout file named ‘myvars.lay’ that gives the locations of each variable in the file ‘mydata’.

4. RUN THE SDA ‘Q4TODDL’ PROGRAM TO MAKE A DDL FILE

The process includes the following steps:

• Change to the directory containing the instrument files, using a command like this:

  
  cd \xstudy\e-inst
  
  

• Create a file of commands (here named ‘q4toddl.txt’)

  With any text editor that creates a plain ASCII file, create a file containing commands that specify the desired options for Q4TODDL. Any name will do for the file; in this example we will call the command file ‘q4toddl.txt’. An example that will cover most situations is the following:

  
  #_____(Command file for Q4TODDL -- named ‘q4toddl.txt’)__________
  
  # Note that lines beginning with ‘#’ are interpreted as comments.
  # Begin the commands in column 1 of your file.
  
  #
  # The first command is a list of .q or .m files used by CASES
  QFiles = file1.q file2.q
  Varlist = myvars
  Layout = myvars.lay
  Output = myddl.txt
  
  
  #__________(End of command file)_________________________________
  
  

  The above command file will work fine, assuming that the list of variables you want is in ‘myvars’ and your layout file is ‘myvars.lay’, and you are running the Q4TODDL program in the same directory as the ‘.q’ files (or the macro-expanded ‘.m’ files). (For more options and explanations, see the full Q4TODDL document.)

  The DDL output will be written to the file ‘myddl.txt’, which was the name specified in the command file.

• Run the Q4TODDL program, giving the name of the command file after the ‘-b’ flag.

  q4toddl -b q4toddl.txt
  

  This command will create a DDL file (named ‘myddl.txt’ in the command file).

• Examine the diagnostic output

  Diagnostic and error messages are appended to the file ‘Q4TODDL.MSG’. It is always a good idea to take a look at that file.

5. ADD STUDY-LEVEL INFORMATION TO THE DDL FILE

The main required elements are:

• A study title: title= ...

• The number of characters in each data record or line:
  reclen = xxx

• If the data file contains more than one record per case, you must indicate that as well:
  records/case = n

• The first variable definition after the study-level information MUST be a variable named ’CASEID’. You can edit the location and description of a suitable variable into the blank field produced by Q4TODDL.

For a complete description of the required format of a DDL file, see the DDL document.

6. CHECK THE DDL FILE

For a DDL file named ’myddl.txt’, you would give the following command:

makesda -c -l myddl.txt

Once you have a DDL file without errors, you can proceed to create an SDA dataset and generate a codebook.

SEE ALSO: