Processes | 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:
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All of the variables in the specified data set are displayed in the Available Variables field.
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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.