Parameters | Expression Parameters | By Variables for Loess Normalization

By Variables for Loess Normalization
Use this field to specify variables that define separate groups of rows for which to compute a loess curve (Print-Tip, for example). A distinct loess curve is fit to rows in each group.
Use this option to perform print-tip loess normalization. To do this, you must define a column in the input data set that indicates the print-tip used for each spot.
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.
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 for Loess Normalization field.
Note: If no BY variables are specified, the analysis is conducted across all the subjects.