xgbse._kaplan_neighbors.XGBSEKaplanNeighbors¶
Convert xgboost into a nearest neighbor model, where we use hamming distance to define similar elements as the ones that co-ocurred the most at the ensemble terminal nodes.
Then, at each neighbor-set compute survival estimates with the Kaplan-Meier estimator.
Note
-
We recommend using dart as the booster to prevent any tree to dominate variance in the ensemble and break the leaf co-ocurrence similarity logic.
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This method can be very expensive at scales of hundreds of thousands of samples, due to the nearest neighbor search, both on training (construction of search index) and scoring (actual search).
Read more in How XGBSE works.
__init__(self, xgb_params=None, n_neighbors=30, radius=None)
special
¶
Parameters:
Name | Type | Description | Default |
---|---|---|---|
xgb_params |
Dict |
Parameters for XGBoost model. If not passed, the following default parameters will be used:
Check https://xgboost.readthedocs.io/en/latest/parameter.html for more options. |
None |
n_neighbors |
Int |
Number of neighbors for computing KM estimates |
30 |
radius |
Float |
If set, uses a radius around the point for neighbors search |
None |
fit(self, X, y, num_boost_round=1000, validation_data=None, early_stopping_rounds=None, verbose_eval=0, persist_train=True, index_id=None, time_bins=None)
¶
Transform feature space by fitting a XGBoost model and outputting its leaf indices. Build search index in the new space to allow nearest neighbor queries at scoring time.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
X |
[pd.DataFrame, np.array] |
Design matrix to fit XGBoost model |
required |
y |
structured array(numpy.bool_, numpy.number |
Binary event indicator as first field, and time of event or time of censoring as second field. |
required |
num_boost_round |
Int |
Number of boosting iterations. |
1000 |
validation_data |
Tuple |
Validation data in the format of a list of tuples [(X, y)] if user desires to use early stopping |
None |
early_stopping_rounds |
Int |
Activates early stopping. Validation metric needs to improve at least once in every early_stopping_rounds round(s) to continue training. See xgboost.train documentation. |
None |
verbose_eval |
[Bool, Int] |
Level of verbosity. See xgboost.train documentation. |
0 |
persist_train |
Bool |
Whether or not to persist training data to use explainability through prototypes |
True |
index_id |
pd.Index |
User defined index if intended to use explainability through prototypes |
None |
time_bins |
np.array |
Specified time windows to use when making survival predictions |
None |
Returns:
Type | Description |
---|---|
XGBSEKaplanNeighbors |
Fitted instance of XGBSEKaplanNeighbors |
predict(self, X, time_bins=None, return_ci=False, ci_width=0.683, return_interval_probs=False)
¶
Make queries to nearest neighbor search index build on the transformed XGBoost space. Compute a Kaplan-Meier estimator for each neighbor-set. Predict the KM estimators.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
X |
pd.DataFrame |
Dataframe with samples to generate predictions |
required |
time_bins |
np.array |
Specified time windows to use when making survival predictions |
None |
return_ci |
Bool |
Whether to return confidence intervals via the Exponential Greenwood formula |
False |
ci_width |
Float |
Width of confidence interval |
0.683 |
return_interval_probs |
Bool |
Boolean indicating if interval probabilities are supposed to be returned. If False the cumulative survival is returned. |
False |
Returns:
Type | Description |
---|---|
(pd.DataFrame) |
A dataframe of survival probabilities for all times (columns), from a time_bins array, for all samples of X (rows). If return_interval_probs is True, the interval probabilities are returned instead of the cumulative survival probabilities. upper_ci (np.array): Upper confidence interval for the survival probability values lower_ci (np.array): Lower confidence interval for the survival probability values |