SDA 3.5 Documentation for SUBSET

NAME

subset - Make a subset of an SDA dataset

USAGE

subset -b filename

DESCRIPTION

The subset program can create a data file that contains only a subset of the variables and/or cases in an SDA dataset. The program also generates a matching DDL file.

The output data file is an ASCII fixed-column file with one record per case, with an optional delimiter (blank or comma) between variables on the same record. A header record with variable names is also output, if the selected output format is a comma separated values (CSV) file. For more information on the various output data formats, see the appropriate section in the online help file for the subset program.

Ordinarily this program is invoked by the Web interface for the SDA programs, and the user does not have to deal with the keywords given in this document. However, it is possible to run this procedure directly in batch mode, by preparing a command file which specifies the variables to be included in the subset and the options to use. This document explains how to prepare such a file.

-b filename: The name of the batch command file is specified to the program after the ‘-b’ flag.

KEYWORDS

The batch command file contains specifications for the subset. These specifications are given in the form "keyword = something" with one keyword per line. Keywords may be given in any order, either in upper or in lower case. The valid keywords are as follows (with significant characters shown in capital letters):

=============================


Keyword       Possible Specification          Default (if no keyword)
_____________________________________________________________________

Specify ONE of the following two data sources


STUdy=        path of dataset directory       Required for subset from
                (can be repeated)               SDA dataset

INDATa=       path of ASCII data file         No subset from ASCII file
INDDL=        path of DDL file                No subset from ASCII file
                (specify both data and DDL)

Other specifications


Filter=       name(s) and codes of filter     No filter
                variable(s)

VARList=      path of file with list of       REQUIRED
                variables to output

TYPE=         type of data file to produce    TEXT
               -TEXT: text file, no blanks
               -TEXTBL: text file with a
                 blanks between vars
               -CSV: comma separated values


OUTDATa=      filename for output data        outdata.txt
               (overwrite existing file)

OUTDDL=       filename for output DDL         outddl.txt
               (overwrite existing file)

WEBMSGfile=   filename to capture output      No record of user messages
                displayed to Web users of
                the subset procedure

NOTES

Source of the data
The source of the data to subset may be specified EITHER as:
1. an SDA dataset (or multiple SDA datasets, if there are recoded and computed variables), OR
2. a text (ASCII) data file plus a DDL file.
Order of the variables
The variables to be included in the subset are output to the data file in the order specified in the ’varlist’ file.
Codebook
When the subset procedure is run from the Web interface, a simple ASCII codebook can be produced, because the Web version can invoke the SDA xcodebk program, together with the generated DDL file. The batch subset procedure does not do that automatically, but you can run the ‘xcodebk’ program yourself in batch mode, if you need a codebook.
Data definitions for SAS, SPSS, and Stata
When the subset procedure is run from the Web interface, data definitions or metadata for SAS, SPSS, Stata, and DDI (version 2) can be produced, because the Web version can invoke the SDA ddltox program, together with the generated DDL file. The batch subset procedure does not do that automatically, but you can run the ‘ddltox’ program yourself in command-line mode, if you need data definitions for one or more of those programs.

EXAMPLE

Simple example of a batch command file

The SDA dataset is in the directory ’/sa/sdatest’. The results will overwrite the output data and DDL files if the files already exist.


     study = /sa/sdatest
     varlist = mylist.txt
     outdata = mydata.txt
     outddl = myddl.txt

Example of a file containing a variable list

(Variable names are separated by spaces, commas, or are on new lines.)

     CASEID age educ gender
     spend, spend2, spend3 spend4

CSM, UC Berkeley
April 12, 2011