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The LOGISTIC Procedure


PROC LOGISTIC < options >;
The PROC LOGISTIC statement starts the LOGISTIC procedure and optionally identifies input and output data sets, controls the ordering of the response levels, and suppresses the display of results.

adds the estimated covariance matrix to the OUTEST= data set. For the COVOUT option to have an effect, the OUTEST= option must be specified. See the section "OUTEST= Output Data Set" for more information.

names the SAS data set containing the data to be analyzed. If you omit the DATA= option, the procedure uses the most recently created SAS data set.

reverses the sorting order for the levels of the response variable. If both the DESCENDING and ORDER= options are specified, PROC LOGISTIC orders the levels according to the ORDER= option and then reverses that order. See the "Response Level Ordering" section for more detail.

INEST= SAS-data-set
names the SAS data set that contains initial estimates for all the parameters in the model. BY-group processing is allowed in setting up the INEST= data set. See the section "INEST= Data Set" for more information.

specifies the length of effect names in tables and output data sets to be n characters, where n is a value between 20 and 200. The default length is 20 characters.

suppresses all displayed output. Note that this option temporarily disables the Output Delivery

System (ODS); see Chapter 15, "Using the Output Delivery System," for more information.

specifies the sorting order for the levels of the response variable. When ORDER=FORMATTED (the default) for numeric variables for which you have supplied no explicit format (that is, for which there is no corresponding FORMAT statement in the current PROC LOGISTIC run or in the DATA step that created the data set), the levels are ordered by their internal (numeric) value. Note that this represents a change from previous releases for how class levels are ordered. In releases previous to Version 8, numeric class levels with no explicit format were ordered by their BEST12. formatted values, and in order to revert to the previous ordering you can specify this format explicitly for the affected classification variables. The change was implemented because the former default behavior for ORDER=FORMATTED often resulted in levels not being ordered numerically and usually required the user to intervene with an explicit format or ORDER=INTERNAL to get the more natural ordering. The following table shows how PROC LOGISTIC interprets values of the ORDER= option.

Value of ORDER= Levels Sorted By
DATAorder of appearance in the input data set
FORMATTEDexternal formatted value, except for numeric
 variables with no explicit format, which are
 sorted by their unformatted (internal) value
FREQdescending frequency count; levels with the
 most observations come first in the order
INTERNALunformatted value

By default, ORDER=FORMATTED. For FORMATTED and INTERNAL, the sort order is machine dependent. For more information on sorting order, see the chapter on the SORT procedure in the SAS Procedures Guide and the discussion of BY-group processing in SAS Language Reference: Concepts.

OUTEST= SAS-data-set
creates an output SAS data set that contains the final parameter estimates and, optionally, their estimated covariances (see the preceding COVOUT option). The names of the variables in this data set are the same as those of the explanatory variables in the MODEL statement plus the name Intercept for the intercept parameter in the case of a binary response model. For an ordinal response model with more than two response categories, the parameters are named Intercept, Intercept2, Intercept3, and so on. The output data set also includes a variable named _LNLIKE_, which contains the log likelihood.

See the section "OUTEST= Output Data Set" for more information.

displays simple descriptive statistics (mean, standard deviation, minimum and maximum) for each explanatory variable in the MODEL statement. The SIMPLE option generates a breakdown of the simple descriptive statistics for the entire data set and also for individual response levels. The NOSIMPLE option suppresses this output and is the default.

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Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.