r-cran-recipes 0.1.0-1 / usr / lib / R / site-library / recipes / doc / Ordering.Rmd

---
title: "Ordering of Steps"
vignette: >
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteIndexEntry{Ordering of Steps}
output:
  knitr:::html_vignette:
    toc: yes
---

In recipes, there are no constraints related to the order in which steps are added to the recipe. However, there are some general suggestions that you should consider:

* If using a Box-Cox transformation, don't center the data first or do any operations that might make the data non-positive. Alternatively, use the Yeo-Johnson transformation so you don't have to worry about this. 
* Recipes do not automatically create dummy variables (unlike _most_ formula methods). If you want to center, scale, or do any other operations on _all_ of the predictors, run `step_dummy` first so that numeric columns are in the data set instead of factors. 
* As noted in the help file for `step_interact`, you should make dummy variables _before_ creating the interactions.
* If you are lumping infrequently categories together with `step_other`, call `step_other` before `step_dummy`.

While your project's needs may vary, here is a suggested order of _potential_ steps that should work for most problems:

1. Impute
1. Individual transformations for skewness and other issues
1. Discretize (if needed and if you have no other choice) 
1. Create dummy variables
1. Create interactions
1. Normalization steps (center, scale, range, etc) 
1. Multivariate transformation (e.g. PCA, spatial sign, etc) 

Again, your milage may vary for your particular problem.