VARIABLES Statement
- VARIABLES / options ;
The VARIABLES statement specifies the variable lists in
the input data sets. This statement is optional but if it
is used, it must appear immediately after the
PROC DTREE statement.
The options that can appear in the VARIABLES statement are divided into
groups according to the data set in which they occur.
Table 3.25 lists
all the variables or variable lists associated with each input data
set and their types. It also lists the default variables if they are
not specified in this statement.
Table 3.25: Input Data Sets and Their Associated Variables
|
Data Set
|
Variable
|
Type*
|
Interpretation
|
Default
|
| STAGEIN= | OUTCOME= | C/N | Outcome names | Variables with prefix _OUT |
| | REWARD= | N | Instant reward | Variables with prefix _REW |
| | STAGE= | C/N | Stage name | _STNAME_ |
| | SUCCESSOR= | as STAGE= | Immediate successors | Variables with prefix _SUCC |
| | TYPE= | C/N | Stage type | _STTYPE_ |
| | WEB= | C | HTML page for the stage | |
| PROBIN= | EVENT= | as OUTCOME= | Event names | Variables with prefix _EVEN |
| | GIVEN= | as OUTCOME= | Names of given outcomes | Variables with prefix _GIVE |
| | PROB= | N | Conditional probabilities | Variables with prefix _PROB |
| PAYOFFS= | ACTION= | as OUTCOME= | Action names of final decision | Variables with prefix _ACT |
| | STATE= | as OUTCOME= | Outcome names | Variables with prefix _STAT |
| | VALUE= | N | Values of the scenario | Variables with prefix _VALU |
The following options specify the variables or variable lists in the
STAGEIN= input data set that identify the stage name,
its type, its
outcomes, and the reward; and the immediate successor of each outcome
for each stage in the decision model:
-
OUTCOME=(variables)
-
identifies all variables in the STAGEIN= data set
that contain the outcome names of the stage specified by the
STAGE= variable.
If the OUTCOME= option is not specified, PROC DTREE looks for
the default variable names that have the prefix _OUT in the data set.
It is necessary to have at least one OUTCOME= variable in the
STAGEIN= data set.
The OUTCOME= variables can be either all character or all numeric.
You cannot mix character and numeric variables as outcomes.
-
REWARD=(variables)
- COST=(variables)
-
identifies all variables in the STAGEIN= data set
that contain the reward for each outcome specified by the
OUTCOME= variables.
If the REWARD= option is not specified, PROC DTREE looks for
the default variable names that have the prefix
_REW in the data set.
The number of REWARD= variables must be equal to the number of
OUTCOME=
variables in the data set. The REWARD= variables must have numeric
values.
-
STAGE=variable
-
specifies the variable in the STAGEIN= data set
that names the
stages in the decision model. If the STAGE= option is omitted,
PROC DTREE looks for the default variable named _STNAME_ in the
data set. The STAGE= variable must be specified if the data set does
not contain a variable named _STNAME_. The STAGE= variable can be
either character or numeric.
- SUCCESSOR=(variables)
- SUCC=(variables)
-
identifies all variables in the STAGEIN= data set that
contain the names of immediate successors (another stage) of each
outcome specified by the OUTCOME= variables.
These variables must be
of the same type and length as those defined in the
STAGE= option. If the
SUCCESSOR= option
is not specified, PROC DTREE looks for the default variable names
that have the prefix _SUCC in the data set. The number of SUCCESSOR=
variables must be equal to the number of OUTCOME= variables.
The values of SUCCESSOR= variables must be stage names (values
of STAGE= variables in the same data set).
- TYPE=variable
-
identifies the variable in the STAGEIN= data set
that contains
the type identifier of the stage specified by the
STAGE= variable.
If the TYPE= option is omitted, PROC DTREE looks for the default
variable named _STTYPE_ in the data set. The TYPE= variable
must be specified if the data set does not contain a variable named
_STTYPE_. The STAGE= variable can be
either character or numeric.
The following are valid values for the TYPE= variable
|
Value
|
Description
|
| DECISION | or | D | or | 1 | identifies the stage as a decision stage |
| CHANCE | or | C | or | 2 | identifies the stage as an uncertain stage |
| END | or | E | or | 3 | identifies the stage as an end stage |
It is not necessary to specify an end stage in the
STAGEIN= data set.
- WEB=variable
- HTML=variable
-
specifies the character variable in the STAGEIN=
data set that identifies an HTML page for each stage. The procedure
generates an HTML image map using this information for all the decision
tree nodes corresponding to a stage.
The following options specify the variables or variable lists in the
PROBIN= input data set that identify the
given outcome names, the event
(outcome) name, and the conditional probability for each outcome of a
chance stage.
- EVENT=(variables)
-
identifies all variables in the PROBIN= data set
that contain
the names of events (outcomes) that probabilities depend on the
outcomes specified by the GIVEN= variables.
If the EVENT= option
is not specified, PROC DTREE looks for the default variable names
that have the prefix _EVEN in the data set. You must have
at least one EVENT= variable in the PROB= data set.
The values of
EVENT= variables must be outcome names that are specified in the
STAGEIN= data set.
- GIVEN=(variables)
-
identifies all variables in the PROBIN= data set
that contain
the given condition (a list of outcome names) of a chance stage on
which the probabilities of the outcome depend. If the
GIVEN= option is not specified, PROC DTREE looks for the default
variable names that have the prefix _GIVE in the data set. It is not
necessary to have GIVEN= variables in the data set but if there are
any, their values must be outcome names that are specified in the
STAGEIN=
data set.
- PROB=(variables)
-
identifies all variables in the PROBIN= data set
that contain
the values of the conditional probability of each event specified
by the EVENT= variables, given that
the outcomes specified by
the GIVEN= variables have occurred.
If the PROB= option is not
specified, PROC DTREE looks for the default variable names that
have the prefix _PROB in the data set. The number of PROB= variables
in the data set must be equal to the number of
EVENT= variables. The
PROB= variables must have numeric values between 0 and 1
inclusive.
The following options specify the variables or variable lists in the
PAYOFFS= input data set that identify
the possible scenarios (a
sequence of outcomes), the final outcome names, and the evaluating values
(payoff) of combinations of scenarios and final outcomes.
- ACTION=(variables)
-
identifies all variables in the PAYOFFS= data set
that contain
the name of the final outcome for each possible scenario. If the
ACTION= option is not specified, PROC DTREE looks for the
default variable names that have the prefix _ACT in the data set.
It is not necessary to have any ACTION= variables in the PAYOFFS=
data set, but if there are any, their values must be outcome names
specified in the STAGEIN= data set.
- STATE=(variables)
-
identifies all variables in the PAYOFFS= data set
that contain
the names of outcomes that identify a possible scenario (a sequence
of outcomes or a path in the decision tree), or the names of outcomes
which combine with every outcome specified by the
ACTION= variables
to identify a possible scenario. If the STATE= option is not
specified, PROC DTREE looks for the default variable names that
have the prefix _STAT in the data set. It is not necessary to have
any STATE= variables in the PAYOFFS= data set, but if there are any,
their values must
be outcome names specified in the STAGEIN= data set.
- VALUE=(variables)
- PAYOFFS=(variables)
- UTILITY=(variables)
- LOSS=(variables)
-
identifies all variables in the PAYOFFS= data set
that contain
the evaluating values or payoffs for all possible scenarios
identified by the outcomes specified by the STATE=
variables and the
outcomes specified by the associated ACTION=
variables. If the
VALUE= option is not specified, PROC DTREE looks for the
default variable names that have the prefix _VALU in the data set.
The number of VALUE= variables must be equal to the number of
ACTION=
variables if there are any ACTION= variables.
If there are no ACTION= variables
in the data set, at least one STATE= variable
must be in the data set,
and the number of VALUE= variables must be exactly 1. The VALUE=
variables must have numeric values.
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
