ml_decision_tree: Decision Tree Model for Regression and Classification

In danzafar/tidyspark: A Tidy Interface to Spark

Description

ml_decision_tree fits a Decision Tree Regression model or Classification model on a spark_tbl. Users can call summary to get a summary of the fitted Decision Tree model, predict to make predictions on new data, and write_ml/read_ml to save/load fitted models. For more details, see Decision Tree Regression and Decision Tree Classification

Usage

ml_decision_tree(
  data,
  formula,
  type = c("regression", "classification"),
  maxDepth = 5,
  maxBins = 32,
  impurity = NULL,
  seed = NULL,
  minInstancesPerNode = 1,
  minInfoGain = 0,
  checkpointInterval = 10,
  maxMemoryInMB = 256,
  cacheNodeIds = FALSE,
  handleInvalid = c("error", "keep", "skip")
)

## S4 method for signature 'DecisionTreeRegressionModel'
summary(object)

## S3 method for class 'summary.DecisionTreeRegressionModel'
print(x, ...)

## S4 method for signature 'DecisionTreeClassificationModel'
summary(object)

## S3 method for class 'summary.DecisionTreeClassificationModel'
print(x, ...)

## S4 method for signature 'DecisionTreeRegressionModel'
predict(object, newData)

## S4 method for signature 'DecisionTreeClassificationModel'
predict(object, newData)

## S4 method for signature 'DecisionTreeRegressionModel,character'
write_ml(object, path, overwrite = FALSE)

## S4 method for signature 'DecisionTreeClassificationModel,character'
write_ml(object, path, overwrite = FALSE)

Arguments

data	a spark_tbl for training.
formula	a symbolic description of the model to be fitted. Currently only a few formula operators are supported, including '~', ':', '+', and '-'.
type	type of model, one of "regression" or "classification", to fit
maxDepth	Maximum depth of the tree (>= 0).
maxBins	Maximum number of bins used for discretizing continuous features and for choosing how to split on features at each node. More bins give higher granularity. Must be >= 2 and >= number of categories in any categorical feature.
impurity	Criterion used for information gain calculation. For regression, must be "variance". For classification, must be one of "entropy" and "gini", default is "gini".
seed	integer seed for random number generation.
minInstancesPerNode	Minimum number of instances each child must have after split.
minInfoGain	Minimum information gain for a split to be considered at a tree node.
checkpointInterval	Param for set checkpoint interval (>= 1) or disable checkpoint (-1). Note: this setting will be ignored if the checkpoint directory is not set.
maxMemoryInMB	Maximum memory in MB allocated to histogram aggregation.
cacheNodeIds	If FALSE, the algorithm will pass trees to executors to match instances with nodes. If TRUE, the algorithm will cache node IDs for each instance. Caching can speed up training of deeper trees. Users can set how often should the cache be checkpointed or disable it by setting checkpointInterval.
handleInvalid	How to handle invalid data (unseen labels or NULL values) in features and label column of string type in classification model. Supported options: "skip" (filter out rows with invalid data), "error" (throw an error), "keep" (put invalid data in a special additional bucket, at index numLabels). Default is "error".
object	A fitted Decision Tree regression model or classification model.
x	summary object of Decision Tree regression model or classification model returned by summary.
...	additional arguments passed to the method.
newData	a spark_tbl for testing.
path	The directory where the model is saved.
overwrite	Overwrites or not if the output path already exists. Default is FALSE which means throw exception if the output path exists.

Value

ml_decision_tree returns a fitted Decision Tree model.

summary returns summary information of the fitted model, which is a list. The list of components includes formula (formula), numFeatures (number of features), features (list of features), featureImportances (feature importances), and maxDepth (max depth of trees).

predict returns a spark_tbl containing predicted labeled in a column named "prediction".

Note

ml_decision_tree since 2.3.0

summary(DecisionTreeRegressionModel) since 2.3.0

print.summary.DecisionTreeRegressionModel since 2.3.0

summary(DecisionTreeClassificationModel) since 2.3.0

print.summary.DecisionTreeClassificationModel since 2.3.0

predict(DecisionTreeRegressionModel) since 2.3.0

predict(DecisionTreeClassificationModel) since 2.3.0

write_ml(DecisionTreeRegressionModel, character) since 2.3.0

write_ml(DecisionTreeClassificationModel, character) since 2.3.0

Examples

## Not run: 
# fit a Decision Tree Regression Model
df <- spark_tbl(longley)
model <- df %>%
  ml_decision_tree(Employed ~ ., type = "regression",
                   maxDepth = 5, maxBins = 16)

# get the summary of the model
summary(model)

# make predictions
predictions <- predict(model, df)

# save and load the model
path <- "path/to/model"
write_ml(model, path)
savedModel <- read_ml(path)
summary(savedModel)

# fit a Decision Tree Classification Model
t <- as.data.frame(Titanic)
df <- spark_tbl(t)
model <- ml_decision_tree(df, Survived ~ Freq + Age, "classification")

## End(Not run)

danzafar/tidyspark documentation built on Sept. 30, 2020, 12:19 p.m.