explain_xgboost: Create explainer from your xgboost model

In DALEXtra: Extension for 'DALEX' Package

Create explainer from your xgboost model

Description

DALEX is designed to work with various black-box models like tree ensembles, linear models, neural networks etc. Unfortunately R packages that create such models are very inconsistent. Different tools use different interfaces to train, validate and use models. One of those tools, we would like to make more accessible is the xgboost package.

Usage

explain_xgboost(
  model,
  data = NULL,
  y = NULL,
  weights = NULL,
  predict_function = NULL,
  predict_function_target_column = NULL,
  residual_function = NULL,
  ...,
  label = NULL,
  verbose = TRUE,
  precalculate = TRUE,
  colorize = !isTRUE(getOption("knitr.in.progress")),
  model_info = NULL,
  type = NULL,
  encode_function = NULL,
  true_labels = NULL
)

Arguments

model	object - a model to be explained
data	data.frame or matrix - data which will be used to calculate the explanations. If not provided, then it will be extracted from the model. Data should be passed without a target column (this shall be provided as the y argument). NOTE: If the target variable is present in the data, some of the functionalities may not work properly.
y	numeric vector with outputs/scores. If provided, then it shall have the same size as data
weights	numeric vector with sampling weights. By default it's NULL. If provided, then it shall have the same length as data
predict_function	function that takes two arguments: model and new data and returns a numeric vector with predictions. By default it is yhat.
predict_function_target_column	Character or numeric containing either column name or column number in the model prediction object of the class that should be considered as positive (i.e. the class that is associated with probability 1). If NULL, the second column of the output will be taken for binary classification. For a multiclass classification setting, that parameter cause switch to binary classification mode with one vs others probabilities.
residual_function	function that takes four arguments: model, data, target vector y and predict function (optionally). It should return a numeric vector with model residuals for given data. If not provided, response residuals (y-\hat{y}) are calculated. By default it is residual_function_default.
...	other parameters
label	character - the name of the model. By default it's extracted from the 'class' attribute of the model
verbose	logical. If TRUE (default) then diagnostic messages will be printed
precalculate	logical. If TRUE (default) then predicted_values and residual are calculated when explainer is created. This will happen also if verbose is TRUE. Set both verbose and precalculate to FALSE to omit calculations.
colorize	logical. If TRUE (default) then WARNINGS, ERRORS and NOTES are colorized. Will work only in the R console. Now by default it is FALSE while knitting and TRUE otherwise.
model_info	a named list (package, version, type) containing information about model. If NULL, DALEX will seek for information on it's own.
type	type of a model, either classification or regression. If not specified then type will be extracted from model_info.
encode_function	function(data, ...) that if executed with data parameters returns encoded dataframe that was used to fit model. Xgboost does not handle factors on it's own so such function is needed to acquire better explanations.
true_labels	a vector of y before encoding.

Value

explainer object (explain) ready to work with DALEX

Examples

library("xgboost")
library("DALEXtra")
library("mlr")
# 8th column is target that has to be omitted in X data
data <- as.matrix(createDummyFeatures(titanic_imputed[,-8]))
model <- xgboost(data, titanic_imputed$survived, nrounds = 10,
                 params = list(objective = "binary:logistic"),
                prediction = TRUE)
# explainer with encode functiom
explainer_1 <- explain_xgboost(model, data = titanic_imputed[,-8],
                               titanic_imputed$survived,
                               encode_function = function(data) {
 as.matrix(createDummyFeatures(data))
})
plot(predict_parts(explainer_1, titanic_imputed[1,-8]))

# explainer without encode function
explainer_2 <- explain_xgboost(model, data = data, titanic_imputed$survived)
plot(predict_parts(explainer_2, data[1,,drop = FALSE]))

DALEXtra documentation built on May 31, 2023, 5:30 p.m.