This is due to a difference in data quality. The CYP2D6 model is categorical due to an uneven distribution in Ki values in the data set and uncertainty regarding the purity of some compounds going into the assay. The CYP2C9 data was more robust, lending itself to a continuous model.

You can find information on the models in Section 17 of the StarDrop Reference Guide, which can be accessed via the Help menu in StarDrop.

Experimental data is used to create the models and this process is described in detail in this section.

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