GDA Syntax - Overview

The GDA syntax consists of command lines, which are terminated by semicolons. The complete command syntax for GDA is shown below. Note that terms in curly brackets ({}) denote alternate specifications (e.g., MBUILD = ALL or MBUILD = BESTSUBSET); optional keywords are enclosed in brackets ([]); all keywords are shown in upper case letters (even thought the syntax interpreter is not case sensitive).

GDA, GRM and GLM syntax conventions
The GDA syntax conventions are essentially identical to the GLM syntax conventions and the GRM syntax conventions (see General Linear Models (GLM), and General Regression Models (GRM), with only a few additions and omissions relating to the specification of the categorical dependent variable, and for the available methods for best subset selection of predictor effects. The following is a list of keywords available in GDA; note that the Generalized Linear/Nonlinear Models (GLZ) and Partial Least Squares (PLS) modules also use similar syntax, with sets of additional keywords (options) that are specific to those particular applications.

GDA

DEPENDENT [=] { Variable [(Value List)]};
[PRIORS [=] { ESTIMATED };
    { EQUAL };
    { USER (Value List) };]
[GROUPS [=] { NONE };
    { Variable [(Value List)]
    .......
    Variable [(Value List)] };]
[COVARIATE [=] { NONE };
    { Variable List };]
[DESIGN [=] { NONE };
    { Effects };]
[SDELTA [=] { Value };]
[IDELTA [=] { Value };]
[SURFACE [=] { NONE }
    { Covariate Variable List };]
[SAMPLE [=] { NONE }
    { Variable (Value) };]
[MBUILD [=] { all }
    { FORWARD };
    { BACKWARD };
    { FSTEPWISE };
    { BSTEPWISE };
    { BESTSUBSET };]
[FORCE [=] Integer Value;]
[MAXSTEP [=] Integer Value;]
[P1ENTER [=] Value;]
[P2REMOVE [=] Value;]
[F1ENTER [=] Value;]
[F2REMOVE [=] Value;]
[STEPCRIT [=] { P }
    { F }]
[BESTCRIT [=] { LAMBDA }
    { MISCLASS }
    { CROSSVAL };]
[START [=] Integer Value;]
[STOP [=] Integer Value;]
[MAXSUB [=] Integer Value;]
[OUTPUT [=] { NONE }
    { List of options (integers) };]

To learn more about each keyword, click on it.

Example
Shown below is an example specification for a stepwise analysis that includes two categorical predictors and their interaction, as well as continuous predictor variables (use example datafile Exp.sta to run this examples).

GDA

DEPENDENT = TIME;
GROUPS = GROUP GENDER;
COVARIATE = CORRECT1 CORRECT2 CORRECT3;
DESIGN = CORRECT1+CORRECT2+CORRECT3 + GROUP | GENDER;
MBUILD = FSTEPWISE;
MAXSTEP = 10;
P1ENTER = .10;
P2REMOVE = .10;
STEPCRIT = P;

For more examples, see GDA Syntax Examples .

Upper case and lower case letters
The syntax editor is not case sensitive; i.e., DEPENDENT, dependent, or Dependent are all valid specifications of the same keyword.
Order of keywords
The order of keywords should follow that implied in the complete listing of all keywords shown above. Note that, while most of the options can be specified in any order, the Design statement must follow the Dependent, Groups, and Covariate specifications. In general, when a keyword references a variable or effect previously defined, then that specification must occur before the respective keyword reference.
Comments
You can insert comments into the syntax by placing them in curly brackets (e.g., { This is a comment }), or after a pound sign (e.g., ... # This is a comment; all text starting at the pound sign to the end of the respective line will be treated as a comment). You may place comments in between any keywords of the syntax, and you may include several comment lines. Comments will be ignored when the syntax is parsed.

See also, GDA - Index.