Parameters | Expression Parameters | By Variables

By Variables
Use this field to specify one or more BY variables from the input data set to use in your analysis. Separate analyses are conducted for distinct levels of BY group variables. Separate plots are generated for each BY group.
BY Variables
BY variables are optional (in most processes) variable specifications whose values define groups of observations , such as hour, month, or year. BY variables can enable analyses to be performed separately on different groups as defined by that variable. Choosing a BY variable such as gender, for example, groups the subjects by gender and conducts two separate analyses: one for males and one for females.
Alternatively, specifying a BY variable enables you to animate an image so that you can see how response values change according to some grouping, like over time.
For Row-by-Row Modeling processes like ANOVA , BY variables distinguish groups of data to which separate models are fit. For example, specifying a gene ID as the BY Variable in ANOVA fits an ANOVA model separately to each gene. If no BY variable is specified for these processes, a separate model is fit to data from each row.
To Specify One or More BY Variables:
All of the variables in the specified data set are displayed in the Available Variables field.
Click to add the highlighted variable(s) to the By Variables field, as shown below:
Note : If no BY variables are specified, the analysis is conducted across all the subjects.