Predictor object

A Predictor object holds any machine learning model (mlr, caret, randomForest, ...) and the data to be used for analyzing the model. The interpretation methods in the iml package need the machine learning model to be wrapped in a Predictor object.

Details

A Predictor object is a container for the prediction model and the data. This ensures that the machine learning model can be analyzed in a robust way.

Note: In case of classification, the model should return one column per class with the class probability.

Public fields

data

data.frame
Data object with the data for the model interpretation.

model

(any)
The machine learning model.

batch.size

numeric(1)
The number of rows to be input the model for prediction at once.

class

character(1)
The class column to be returned.

prediction.colnames

character
The column names of the predictions.

prediction.function

function
The function to predict newdata.

task

character(1)
The inferred prediction task: "classification" or "regression".

Methods

Public methods

• Predictor$new()

• Predictor$predict()

• Predictor$print()

• Predictor$clone()

---

Method new()

Create a Predictor object

Usage

Predictor$new(
  model = NULL,
  data = NULL,
  predict.function = NULL,
  y = NULL,
  class = NULL,
  type = NULL,
  batch.size = 1000
)

Arguments

model

any
The machine learning model. Recommended are models from mlr and caret. Other machine learning with a S3 predict functions work as well, but less robust (e.g. randomForest).

data

data.frame
The data to be used for analyzing the prediction model. Allowed column classes are: numeric, factor, integer, ordered and character For some models the data can be extracted automatically. Predictor$new() throws an error when it can't extract the data automatically.

predict.function

function
The function to predict newdata. Only needed if model is not a model from mlr or caret package. The first argument of predict.fun has to be the model, the second the newdata:

function(model, newdata)

y

character(1) | numeric | factor
The target vector or (preferably) the name of the target column in the data argument. Predictor tries to infer the target automatically from the model.

class

character(1)
The class column to be returned. You should use the column name of the predicted class, e.g. class="setosa".

type

character(1))
This argument is passed to the prediction function of the model. For regression models you usually don't have to provide the type argument. The classic use case is to say type="prob" for classification models. Consult the documentation of the machine learning package you use to find which type options you have. If both predict.fun and type are used, then type is passed as an argument to predict.fun.

batch.size

numeric(1)
The maximum number of rows to be input the model for prediction at once. Currently only respected for FeatureImp, Partial and Interaction.

---

Method predict()

Predict new data with the machine learning model.

Usage

Predictor$predict(newdata)

Arguments

newdata

data.frame
Data to predict on.

---

Method print()

Print the Predictor object.

Usage

Predictor$print()

---

Method clone()

The objects of this class are cloneable with this method.

Usage

Predictor$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

library("mlr")
#> Loading required package: ParamHelpers
#> 
#> Attaching package: ‘mlr’
#> The following object is masked from ‘package:yaImpute’:
#> 
#>     impute
#> The following object is masked from ‘package:generics’:
#> 
#>     train
task <- makeClassifTask(data = iris, target = "Species")
learner <- makeLearner("classif.rpart", minsplit = 7, predict.type = "prob")
mod.mlr <- train(learner, task)
mod <- Predictor$new(mod.mlr, data = iris)
mod$predict(iris[1:5, ])
#>   setosa versicolor virginica
#> 1      1          0         0
#> 2      1          0         0
#> 3      1          0         0
#> 4      1          0         0
#> 5      1          0         0

mod <- Predictor$new(mod.mlr, data = iris, class = "setosa")
mod$predict(iris[1:5, ])
#>   setosa
#> 1      1
#> 2      1
#> 3      1
#> 4      1
#> 5      1

library("randomForest")
rf <- randomForest(Species ~ ., data = iris, ntree = 20)


mod <- Predictor$new(rf, data = iris, type = "prob")
mod$predict(iris[50:55, ])
#>   setosa versicolor virginica
#> 1      1       0.00      0.00
#> 2      0       0.95      0.05
#> 3      0       0.95      0.05
#> 4      0       0.95      0.05
#> 5      0       1.00      0.00
#> 6      0       1.00      0.00

# Feature importance needs the target vector, which needs to be supplied:
mod <- Predictor$new(rf, data = iris, y = "Species", type = "prob")