# Workflow Stages

Workflows encompasses the three main stages of the modeling process: pre-processing of data, model fitting, and post-processing of results. This page enumerates the possible operations for each stage that have been implemented to date.

## Pre-processing

The two elements allowed for pre-processing are:

• A standard model formula via add_formula().

• A recipe object via add_recipe().

You can use one or the other but not both.

## Model Fitting

parsnip model specifications are the only option here, specified via add_model().

When using a preprocessor, you may need an additional formula for special model terms (e.g. for mixed models or generalized linear models). In these cases, specify that formula using add_model()’s formula argument, which will be passed to the underlying model when fit() is called.

## Post-processing

Some examples of post-processing the model predictions would be: adding a probability threshold for two-class problems, calibration of probability estimates, truncating the possible range of predictions, and so on.

None of these are currently implemented but will be in coming versions.