microsoftml.rx_fast_trees: Boosted Trees
microsoftml.rx_fast_trees(formula: str, data: [revoscalepy.datasource.RxDataSource.RxDataSource, pandas.core.frame.DataFrame], method: ['binary', 'regression'] = 'binary', num_trees: int = 100, num_leaves: int = 20, learning_rate: float = 0.2, min_split: int = 10, example_fraction: float = 0.7, feature_fraction: float = 1, split_fraction: float = 1, num_bins: int = 255, first_use_penalty: float = 0, gain_conf_level: float = 0, unbalanced_sets: bool = False, train_threads: int = 8, random_seed: int = None, ml_transforms: list = None, ml_transform_vars: list = None, row_selection: str = None, transforms: dict = None, transform_objects: dict = None, transform_function: str = None, transform_variables: list = None, transform_packages: list = None, transform_environment: dict = None, blocks_per_read: int = None, report_progress: int = None, verbose: int = 1, ensemble: microsoftml.modules.ensemble.EnsembleControl = None, compute_context: revoscalepy.computecontext.RxComputeContext.RxComputeContext = None)
Machine Learning Fast Tree
rx_fast_trees is an implementation of FastRank. FastRank is an efficient implementation of the MART gradient boosting algorithm. Gradient boosting is a machine learning technique for regression problems. It builds each regression tree in a step-wise fashion, using a predefined loss function to measure the error for each step and corrects for it in the next. So this prediction model is actually an ensemble of weaker prediction models. In regression problems, boosting builds a series of of such trees in a step-wise fashion and then selects the optimal tree using an arbitrary differentiable loss function.
MART learns an ensemble of regression trees, which is a decision tree with
scalar values in its leaves. A decision (or regression) tree is a
binary tree-like flow chart, where at each interior node one decides which
of the two child nodes to continue to based on one of the feature values
from the input. At each leaf node, a value is returned. In the
interior nodes, the decision is based on the test
"x <= v", where
x is the value of the feature in the input sample and
v is one
of the possible values of this feature. The functions that can be produced
by a regression tree are all the piece-wise constant functions.
The ensemble of trees is produced by computing, in each step, a regression tree that approximates the gradient of the loss function, and adding it to the previous tree with coefficients that minimize the loss of the new tree. The output of the ensemble produced by MART on a given instance is the sum of the tree outputs.
In case of a binary classification problem, the output is converted to a probability by using some form of calibration.
In case of a regression problem, the output is the predicted value of the function.
In case of a ranking problem, the instances are ordered by the output value of the ensemble.
method is set to
"regression", a regression version of
FastTree is used. If set to
"ranking", a ranking version of FastTree
is used. In the ranking case, the instances should be ordered by the output
of the tree ensemble. The only difference in the settings of these
versions is in the calibration settings, which are needed only for
The formula as described in revoscalepy.rx_formula.
Interaction terms and
F() are not currently supported in
A data source object or a character string specifying a .xdf file or a data frame object.
A character string that specifies the type of Fast Tree:
"binary" for the default Fast Tree Binary Classification or
"regression" for Fast Tree Regression.
Specifies the total number of decision trees to create in the ensemble.By creating more decision trees, you can potentially get better coverage, but the training time increases. The default value is 100.
The maximum number of leaves (terminal nodes) that can be created in any tree. Higher values potentially increase the size of the tree and get better precision, but risk overfitting and requiring longer training times. The default value is 20.
Determines the size of the step taken in the direction of the gradient in each step of the learning process. This determines how fast or slow the learner converges on the optimal solution. If the step size is too big, you might overshoot the optimal solution. If the step size is too samll, training takes longer to converge to the best solution.
Minimum number of training instances required to form a leaf. That is, the minimal number of documents allowed in a leaf of a regression tree, out of the sub-sampled data. A ‘split’ means that features in each level of the tree (node) are randomly divided. The default value is 10. Only the number of instances is counted even if instances are weighted.
The fraction of randomly chosen instances to use for each tree. The default value is 0.7.
The fraction of randomly chosen features to use for each tree. The default value is 1.
The fraction of randomly chosen features to use on each split. The default value is 1.
Maximum number of distinct values (bins) per feature. If the
feature has fewer values than the number indicated, each value is placed
in its own bin. If there are more values, the algorithm creates
The feature first use penalty coefficient. This is a form of regularization that incurs a penalty for using a new feature when creating the tree. Increase this value to create trees that don’t use many features. The default value is 0.
Tree fitting gain confidence requirement (should be in the range [0,1)). The default value is 0.
True, derivatives optimized for unbalanced
sets are used. Only applicable when
type equal to
The default value is
The number of threads to use in training. The default value is 8.
Specifies the random seed. The default value is None.
Specifies a list of MicrosoftML transforms to be
performed on the data before training or None if no transforms are
to be performed. See
categorical_hash, for transformations that are supported.
These transformations are performed after any specified Python transformations.
The default value is None.
Specifies a character vector of variable names
to be used in
ml_transforms or None if none are to be used.
The default value is None.
NOT SUPPORTED. Specifies the rows (observations) from the data set that are to be used by the model with the name of a logical variable from the data set (in quotes) or with a logical expression using variables in the data set. For example:
row_selection = "old"will only use observations in which the value of the variable
row_selection = (age > 20) & (age < 65) & (log(income) > 10)only uses observations in which the value of the
agevariable is between 20 and 65 and the value of the
incomevariable is greater than 10.
The row selection is performed after processing any data
transformations (see the arguments
transform_function). As with all expressions,
row_selection can be
defined outside of the function call using the
NOT SUPPORTED. An expression of the form that represents the
first round of variable transformations. As with
row_selection) can be defined
outside of the function call using the
NOT SUPPORTED. A named list that contains objects that can be
The variable transformation function.
A character vector of input data set variables needed for the transformation function.
NOT SUPPORTED. A character vector specifying additional Python packages
(outside of those specified in
be made available and preloaded for use in variable transformation functions.
For example, those explicitly defined in revoscalepy functions via
transform_function arguments or those defined
implicitly via their
row_selection arguments. The
transform_packages argument may also be None, indicating that
no packages outside
RxOptions.get_option("transform_packages") are preloaded.
NOT SUPPORTED. A user-defined environment to serve as a parent to all
environments developed internally and used for variable data transformation.
transform_environment = None, a new “hash” environment with parent
revoscalepy.baseenv is used instead.
Specifies the number of blocks to read for each chunk of data read from the data source.
An integer value that specifies the level of reporting on the row processing progress:
0: no progress is reported.
1: the number of processed rows is printed and updated.
2: rows processed and timings are reported.
3: rows processed and all timings are reported.
An integer value that specifies the amount of output wanted.
0, no verbose output is printed during calculations. Integer
4 provide increasing amounts of information.
Sets the context in which computations are executed, specified with a valid revoscalepy.RxComputeContext. Currently local and revoscalepy.RxInSqlServer compute contexts are supported.
Control parameters for ensembling.
FastTrees object with the trained model.
This algorithm is multi-threaded and will always attempt to load the entire dataset into memory.
''' Binary Classification. ''' import numpy import pandas from microsoftml import rx_fast_trees, rx_predict from revoscalepy.etl.RxDataStep import rx_data_step from microsoftml.datasets.datasets import get_dataset infert = get_dataset("infert") import sklearn if sklearn.__version__ < "0.18": from sklearn.cross_validation import train_test_split else: from sklearn.model_selection import train_test_split infertdf = infert.as_df() infertdf["isCase"] = infertdf.case == 1 data_train, data_test, y_train, y_test = train_test_split(infertdf, infertdf.isCase) trees_model = rx_fast_trees( formula=" isCase ~ age + parity + education + spontaneous + induced ", data=data_train) # RuntimeError: The type (RxTextData) for file is not supported. score_ds = rx_predict(trees_model, data=data_test, extra_vars_to_write=["isCase", "Score"]) # Print the first five rows print(rx_data_step(score_ds, number_rows_read=5))
Not adding a normalizer. Making per-feature arrays Changing data from row-wise to column-wise Beginning processing data. Rows Read: 186, Read Time: 0, Transform Time: 0 Beginning processing data. Processed 186 instances Binning and forming Feature objects Reserved memory for tree learner: 7020 bytes Starting to train ... Not training a calibrator because it is not needed. Elapsed time: 00:00:00.0949161 Elapsed time: 00:00:00.0112103 Beginning processing data. Rows Read: 62, Read Time: 0.001, Transform Time: 0 Beginning processing data. Elapsed time: 00:00:00.0230457 Finished writing 62 rows. Writing completed. Rows Read: 5, Total Rows Processed: 5, Total Chunk Time: 0.001 seconds isCase PredictedLabel Score Probability 0 False False -4.722279 0.131369 1 False False -11.550012 0.009757 2 False False -7.312314 0.050935 3 True True 3.889991 0.825778 4 False False -6.361800 0.072782
''' Regression. ''' import numpy import pandas from microsoftml import rx_fast_trees, rx_predict from revoscalepy.etl.RxDataStep import rx_data_step from microsoftml.datasets.datasets import get_dataset airquality = get_dataset("airquality") import sklearn if sklearn.__version__ < "0.18": from sklearn.cross_validation import train_test_split else: from sklearn.model_selection import train_test_split airquality = airquality.as_df() ###################################################################### # Estimate a regression fast forest # Use the built-in data set 'airquality' to create test and train data df = airquality[airquality.Ozone.notnull()] df["Ozone"] = df.Ozone.astype(float) data_train, data_test, y_train, y_test = train_test_split(df, df.Ozone) airFormula = " Ozone ~ Solar_R + Wind + Temp " # Regression Fast Forest for train data ff_reg = rx_fast_trees(airFormula, method="regression", data=data_train) # Put score and model variables in data frame score_df = rx_predict(ff_reg, data=data_test, write_model_vars=True) print(score_df.head()) # Plot actual versus predicted values with smoothed line # Supported in the next version. # rx_line_plot(" Score ~ Ozone ", type=["p", "smooth"], data=score_df)
'unbalanced_sets' ignored for method 'regression' Not adding a normalizer. Making per-feature arrays Changing data from row-wise to column-wise Beginning processing data. Rows Read: 87, Read Time: 0.001, Transform Time: 0 Beginning processing data. Warning: Skipped 4 instances with missing features during training Processed 83 instances Binning and forming Feature objects Reserved memory for tree learner: 21528 bytes Starting to train ... Not training a calibrator because it is not needed. Elapsed time: 00:00:00.0512720 Elapsed time: 00:00:00.0094435 Beginning processing data. Rows Read: 29, Read Time: 0, Transform Time: 0 Beginning processing data. Elapsed time: 00:00:00.0229873 Finished writing 29 rows. Writing completed. Solar_R Wind Temp Score 0 115.0 7.4 76.0 26.003876 1 307.0 12.0 66.0 18.057747 2 230.0 10.9 75.0 10.896211 3 259.0 9.7 73.0 13.726607 4 92.0 15.5 84.0 37.972855