grayskripko/parsnip

A tidy unified interface to models

parsnip

One issue with different functions available in R that do the same thing is that they can have different interfaces and arguments. For example, to fit a random forest classification model, we might have:

# From randomForest
rf_1 <- randomForest(x, y, mtry = 12, ntree = 2000, importance = TRUE)

# From ranger
rf_2 <- ranger(
  y ~ ., 
  data = dat, 
  mtry = 12, 
  num.trees = 2000, 
  importance = 'impurity'
)

# From sparklyr
rf_3 <- ml_random_forest(
  dat, 
  intercept = FALSE, 
  response = "y", 
  features = names(dat)[names(dat) != "y"], 
  col.sample.rate = 12,
  num.trees = 2000
)

Note that the model syntax is very different and that the argument names (and formats) are also different. This is a pain if you go between implementations.

In this example, the type of model is "random forest" while the mode of the model is "classification" (as opposed to regression, survival analysis, etc).

The idea of parsnip is to:

• Separate the definition of a model from its evaluation.
• Decouple the model specification from the implementation (whether the implementation is in R, spark, or something else). For example, the user would call rand_forest instead of ranger::ranger or other specific packages.
• Harmonize the argument names (e.g. n.trees, ntrees, trees) so that users can remember a single name. This will help across model types too so that trees will be the same argument across random forest as well as boosting or bagging. To install it, use:

require(devtools)
install_github("topepo/parsnip")