Ranger Forest Survival

class skranger.ensemble.RangerForestSurvival(n_estimators=100, *, verbose=False, mtry=0, importance='none', min_node_size=0, max_depth=0, replace=True, sample_fraction=None, keep_inbag=False, inbag=None, split_rule='logrank', num_random_splits=1, alpha=0.5, minprop=0.1, respect_categorical_features=None, scale_permutation_importance=False, local_importance=False, regularization_factor=None, regularization_usedepth=False, holdout=False, oob_error=False, n_jobs=0, seed=42, enable_tree_details=False)[source]

Ranger Random Forest Survival implementation for sci-kit survival.

Provides a sksurv interface to the Ranger C++ library using Cython.

  • n_estimators (int) – The number of tree classifiers to train

  • verbose (bool) – Enable ranger’s verbose logging

  • mtry (int/callable) – The number of features to split on each node. When a callable is passed, the function must accept a single parameter which is the number of features passed, and return some value between 1 and the number of features.

  • importance (str) – One of one of none, impurity, impurity_corrected, permutation.

  • min_node_size (int) – The minimal node size.

  • max_depth (int) – The maximal tree depth; 0 means unlimited.

  • replace (bool) – Sample with replacement.

  • sample_fraction (float) – The fraction of observations to sample. The default is 1 when sampling with replacement, and 0.632 otherwise.

  • keep_inbag (bool) – If true, save how often observations are in-bag in each tree. These will be stored in the ranger_forest_ attribute under the key "inbag_counts".

  • inbag (list) – A list of size n_estimators, containing inbag counts for each observation. Can be used for stratified sampling.

  • split_rule (str) – One of logrank, extratrees, C, or maxstat, default logrank.

  • num_random_splits (int) – The number of random splits to consider for the extratrees splitrule.

  • alpha (float) – Significance threshold to allow splitting for the maxstat split rule.

  • minprop (float) – Lower quantile of covariate distribution to be considered for splitting for maxstat split rule.

  • respect_categorical_features (str) – One of ignore, order, partition. The default is partition for the extratrees splitrule, otherwise the default is ignore.

  • scale_permutation_importance (bool) – For permutation importance, scale permutation importance by standard error as in (Breiman 2001).

  • local_importance (bool) – For permutation importance, calculate and return local importance values as (Breiman 2001).

  • regularization_factor (list) – A vector of regularization factors for the features.

  • regularization_usedepth (bool) – Whether to consider depth in regularization.

  • holdout (bool) – Hold-out all samples with case weight 0 and use these for feature importance and prediction error.

  • oob_error (bool) – Whether to calculate out-of-bag prediction error.

  • n_jobs (int) – The number of threads. Default is number of CPU cores.

  • seed (int) – Random seed value.

  • enable_tree_details (bool) – When True, perform additional calculations for detailing the underlying decision trees. Must be enabled for estimators_ and get_estimator to work. Very slow.

  • n_features_in_ (int) – The number of features (columns) from the fit input X.

  • feature_names_ (list) – Names for the features of the fit input X.

  • ranger_forest_ (dict) – The returned result object from calling C++ ranger.

  • mtry_ (int) – The mtry value as determined if mtry is callable, otherwise it is the same as mtry.

  • sample_fraction_ (float) – The sample fraction determined by input validation.

  • regularization_factor_ (list) – The regularization factors determined by input validation.

  • unordered_feature_names_ (list) – The unordered feature names determined by input validation.

  • split_rule_ (int) – The split rule integer corresponding to ranger enum SplitRule.

  • use_regularization_factor_ (bool) – Input validation determined bool for using regularization factor input parameter.

  • respect_categorical_features_ (str) – Input validation determined string respecting categorical features.

  • importance_mode_ (int) – The importance mode integer corresponding to ranger enum ImportanceMode.

  • feature_importances_ (ndarray) – The variable importances from ranger.

property criterion

Compatibility alias for split rule.

fit(X, y, sample_weight=None, split_select_weights=None, always_split_features=None, categorical_features=None)[source]

Fit the ranger random forest using training data.

  • X (array2d) – training input features

  • y (array2d) – training input targets, rows of (bool, float) representing (survival, time)

  • sample_weight (array1d) – optional weights for input samples

  • split_select_weights (list) – Vector of weights between 0 and 1 of probabilities to select features for splitting. Can be a single vector or a vector of vectors with one vector per tree.

  • always_split_features (list) – Features which should always be selected for splitting. A list of column index values.

  • categorical_features (list) – A list of column index values which should be considered categorical, or unordered.


Extract a single estimator tree from the forest. :param int idx: The index of the tree to extract.


Calculate p-values for variable importances.

Uses the fast method from Janitza et al. (2016).


Get parameters for this estimator.


deep (bool, default=True) – If True, will return the parameters for this estimator and contained subobjects that are estimators.


params – Parameter names mapped to their values.

Return type



Predict risk score.


X (array2d) – prediction input features


Predict cumulative hazard function.


X (array2d) – prediction input features


Predict survival function.


X (array2d) – prediction input features


Set the parameters of this estimator.

The method works on simple estimators as well as on nested objects (such as Pipeline). The latter have parameters of the form <component>__<parameter> so that it’s possible to update each component of a nested object.


**params (dict) – Estimator parameters.


self – Estimator instance.

Return type

estimator instance