ROCvar_listBYstate_var(state_value) /PLOT = { CURVE [(REFERENCE)], NONE } /PRINT = [ SE ] [ COORDINATES ] /CRITERIA = [ CUTOFF({INCLUDE,EXCLUDE}) ] [ TESTPOS ({LARGE,SMALL}) ] [ CI (confidence) ] [ DISTRIBUTION ({FREE, NEGEXPO }) ] /MISSING={EXCLUDE,INCLUDE}

The `ROC`

command is used to plot the receiver operating characteristic curve
of a dataset, and to estimate the area under the curve.
This is useful for analysing the efficacy of a variable as a predictor of a state of nature.

The mandatory `var_list` is the list of predictor variables.
The variable `state_var` is the variable whose values represent the actual states,
and `state_value` is the value of this variable which represents the positive state.

The optional subcommand `PLOT`

is used to determine if and how the `ROC`

curve is drawn.
The keyword `CURVE`

means that the `ROC`

curve should be drawn, and the optional keyword `REFERENCE`

,
which should be enclosed in parentheses, says that the diagonal reference line should be drawn.
If the keyword `NONE`

is given, then no `ROC`

curve is drawn.
By default, the curve is drawn with no reference line.

The optional subcommand `PRINT`

determines which additional
tables should be printed. Two additional tables are available. The
`SE`

keyword says that standard error of the area under the
curve should be printed as well as the area itself. In addition, a
p-value for the null hypothesis that the area under the curve equals
0.5 is printed. The `COORDINATES`

keyword says that a
table of coordinates of the `ROC`

curve should be printed.

The `CRITERIA`

subcommand has four optional parameters:

- The
`TESTPOS`

parameter may be`LARGE`

or`SMALL`

.`LARGE`

is the default, and says that larger values in the predictor variables are to be considered positive.`SMALL`

indicates that smaller values should be considered positive. - The
`CI`

parameter specifies the confidence interval that should be printed. It has no effect if the`SE`

keyword in the`PRINT`

subcommand has not been given. - The
`DISTRIBUTION`

parameter determines the method to be used when estimating the area under the curve. There are two possibilities,*viz*:`FREE`

and`NEGEXPO`

. The`FREE`

method uses a non-parametric estimate, and the`NEGEXPO`

method a bi-negative exponential distribution estimate. The`NEGEXPO`

method should only be used when the number of positive actual states is equal to the number of negative actual states. The default is`FREE`

. - The
`CUTOFF`

parameter is for compatibility and is ignored.

The `MISSING`

subcommand determines whether user missing values are to
be included or excluded in the analysis. The default behaviour is to
exclude them.
Cases are excluded on a listwise basis; if any of the variables in `var_list`
or if the variable `state_var` is missing, then the entire case is
excluded.