The ANOVA Procedure |
PROC ANOVA Statement |
The PROC ANOVA statement starts the ANOVA procedure.
You can specify the following options in the PROC ANOVA statement:
names the SAS data set used by the ANOVA procedure. By default, PROC ANOVA uses the most recently created SAS data set.
requests the multivariate mode of eliminating observations with missing values. If any of the dependent variables have missing values, the procedure eliminates that observation from the analysis. The MANOVA option is useful if you use PROC ANOVA in interactive mode and plan to perform a multivariate analysis.
requests that PROC ANOVA reread the input data set, when necessary, instead of writing the values of dependent variables to a utility file. This option decreases disk space usage at the expense of increased execution times and is useful only in rare situations where disk space is at an absolute premium.
specifies the length of effect names to be characters long, where is a value between 20 and 200 characters. The default length is 20 characters.
suppresses the normal display of results. The NOPRINT option is useful when you want to create only the output data set with the procedure. Note that this option temporarily disables the Output Delivery System
(ODS); see Chapter 20, Using the Output Delivery System, for more information.
specifies the sorting order for the levels of the classification variables (specified in the CLASS statement). This ordering determines which parameters in the model correspond to each level in the data. Note that the ORDER= option applies to the levels for all classification variables. The exception is the default ORDER=FORMATTED for numeric variables for which you have supplied no explicit format. In this case, the levels are ordered by their internal value. Note that this represents a change from previous releases for how classification levels are ordered. In releases previous to Version 8, numeric classification 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 ANOVA interprets values of the ORDER= option.
Value of ORDER= |
Levels Sorted By |
DATA |
order of appearance in the input data set |
FORMATTED |
external formatted value, except for numeric variables with no explicit format, which are sorted by their unformatted (internal) value |
FREQ |
descending frequency count; levels with the most observations come first in the order |
INTERNAL |
unformatted value |
names an output data set that contains sums of squares, degrees of freedom, statistics, and probability levels for each effect in the model. If you use the CANONICAL option in the MANOVA statement and do not use an M= specification in the MANOVA statement, the data set also contains results of the canonical analysis. See the section Output Data Set for more information.
controls the plots produced through ODS Graphics. When ODS Graphics is enabled, the ANOVA procedure can display a grouped box-plot of the input data with groups defined by an effect in the model. Such a plot is produced by default if you have a one-way model, with only a single classification variable, or if you use a MEANS statement. Specify the PLOTS=NONE option in order to prevent these plots from being produced when ODS Graphics is enabled.
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