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modelvars()

Usage:
modelvars(varList [,Model]), varList a vector of integers >= 0, Model a
  CHARACTER scalar
modelvars(y:T or x:T or variates:T or factors:T or all:T [, Model])
modelvars(nx:T or nvariates:T or nfactors:T or hasconst:T [, Model])



Keywords: glm
modelvars(VarList,Model), where VarList is a vector of non-negative
integers, say vector(i1,i2,i3,...), returns a vector or matrix whose
columns are the variables in the model specified by the scalar CHARACTER
variable or quoted string Model.  Variable 0 is the dependent variable
(the variable before '=' in Model) and, if i > 0, variable i is the i-th
variate or factor appearing on the right hand side of Model (after '=').

See topic 'models' for information on specifying Model.

modelvars(y:T,Model) returns a vector or matrix containing the dependent
variable of Model.  This usage yields the same result as modelvars(0,
Model).

modelvars(x:T,Model) returns a vector or matrix containing the
independent variates and factors of on the right hand side of Model.
This yields the same as modelvars(run(nv), Model), where nv is the
number of variates and factors.  When there are no variates and factors
("y=1"), NULL is returned.  See topic 'NULL'.  See keyword 'nx' below
for determining the total number of variates and factors.

modelvars(factors:T,Model) returns a vector or matrix containing the
factors on the right hand side of Model.  When there are no factors in
the model, NULL is returned.  See keyword 'nfactors' below for
determining the total number of factors.

modelvars(variates:T,Model) returns a vector or matrix containing the
variates on the right hand side of Model.  When there are no variates in
the model, NULL is returned.  See keyword 'nvariates' below for
determining the total number of variates.

modelvars(all:T,Model) returns a matrix containing the dependent
variable followed by the independent variates and factors of Model.
Equivalent to this is modelvars(run(0,nv),Model).

When Model is omitted (modelvars(VarList) or modelvars(keyword:T)),
variables are taken from internal copies of the variables in the current
active model.  This allows retrieval of the dependent variable and/or
model variables even if they were temporary variables (their names
started with '@').  When there is no active model but variable STRMODEL
exists, modelvars(keyword:T) and modelvars(VarList) are equivalent to
modelvars(keyword:T,STRMODEL) and modelvars(VarList,STRMODEL).  Here
keyword is one of 'x', 'y', 'factors', 'variates', or 'all'.

Examples:
    modelvars(vector(1,2,0),"y=x+a") is equivalent to hconcat(x,a,y)
    modelvars(x:T,"y=x+a+a.x") is equivalent to hconcat(x,a)
    modelvars(all:T,"y=x1+x2") is equivalent to hconcat(y,x1,x2)

Note: Any variables that are factors are returned unchanged.  This is
very different from xvariables(), which computes dummy X-variables
associated with a factor.

                     Counting Factors and Variables
You can also use modelvars() to determine how many factors and variates
there are in a model or to check whether the constant term is in the
model.  This can be useful in a macro using the results of a GLM command
to do further analyses.

modelvars(nx:T [,Model]) returns the number of independent variates and
factors on the right hand side of Model, that is, what would be computed
by ncols(modelvars(x:T [,Model])).  When there are no variates and
factors ("y=1"), 0 is returned.

modelvars(nfactors:T [,Model]) returns the number of factors on the
right hand side of Model, that is, what would be computed by
ncols(modelvars(factors:T, [,Model])).  When there are no factors 0 is
returned.

modelvars(nvariates:T [,Model]) returns the number of variates on the
right hand side of Model, that is, what would be computed by
ncols(modelvars(variates:T [,Model])).  When there are no variates 0 is
returned.

modelvars(hasconst:T [,Model]) is True if and only if the constant term
is in the model.

Examples:
    modelvars(nfactors:T,"y=x+a+b+a.x") returns 2
    modelvars(nvariates:T,"y=x+a+b+a.x") returns 1
    modelvars(nx:T,"y=x+a+b+a.x") returns 3
    modelvars(hasconst:T, "y=x") returns True
    modelvars(hasconst:T, "y=x-1") returns False

See also topics 'models', varnames(), xvariables().


Gary Oehlert 2003-01-15