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verticapy.machine_learning.vertica.ensemble.XGBRegressor

class verticapy.machine_learning.vertica.ensemble.XGBRegressor(name: str = None, overwrite_model: bool = False, max_ntree: int = 10, max_depth: int = 5, nbins: int = 32, split_proposal_method: Literal['local', 'global'] = 'global', tol: float = 0.001, learning_rate: float = 0.1, min_split_loss: float = 0.0, weight_reg: float = 0.0, sample: float = 1.0, col_sample_by_tree: float = 1.0, col_sample_by_node: float = 1.0)

Creates an XGBRegressor object using the Vertica XGB_REGRESSOR algorithm.

Parameters

name: str, optional

Name of the model. The model is stored in the DB.

overwrite_model: bool, optional

If set to True, training a model with the same name as an existing model overwrites the existing model.

max_ntree: int, optional

Maximum number of trees that can be created.

max_depth: int, optional

aximum depth of each tree, an integer between 1 and 20, inclusive.

nbins: int, optional

Number of bins used to find splits in each column, where more splits leads to a longer runtime but more fine-grained, possibly better splits. Must be an integer between 2 and 1000, inclusive.

split_proposal_method: str, optional

Approximate splitting strategy, either global or local (not yet supported).

tol: float, optional

Approximation error of quantile summary structures used in the approximate split finding method.

learning_rate: float, optional

Weight applied to each tree’s prediction. This reduces each tree’s impact, allowing for later trees to contribute and keeping earlier trees from dominating.

min_split_loss: float, optional

Each split must improve the model’s objective function value by at least this much in order to avoid pruning. A value of 0 is the same as turning off this parameter (trees are still pruned based on positive / negative objective function values).

weight_reg: float, optional

Regularization term that is applied to the weights of the leaves in the regression tree. A higher value leads to more sparse/smooth weights, which often helps to prevent overfitting.

sample: float, optional

Fraction of rows used per iteration in training.

col_sample_by_tree: float, optional

float in the range (0,1] that specifies the fraction of columns (features), chosen at random, to use when building each tree.

col_sample_by_node: float, optional

float in the range (0,1] that specifies the fraction of columns (features), chosen at random, to use when evaluating each split.

Attributes

Many attributes are created during the fitting phase.

trees_: list of BinaryTreeRegressor

Tree models are instances of ` BinaryTreeRegressor, each possessing various attributes. For more detailed information, refer to the documentation for BinaryTreeRegressor.

features_importance_: numpy.array

The importance of features. It is calculated using the average gain of each tree. To determine the final score, VerticaPy sums the scores of each tree, normalizes them and applies an activation function to scale them. It is necessary to use the features_importance() method to compute it initially, and the computed values will be subsequently utilized for subsequent calls.

features_importance_trees_: dict of numpy.array

Each element of the array represents the feature importance of tree i. The importance of features is calculated using the average gain of each tree. It is necessary to use the features_importance() method to compute it initially, and the computed values will be subsequently utilized for subsequent calls.

mean_: float

The mean of the response column.

eta_: float

The learning rate, is a crucial hyperparameter in machine learning algorithms. It determines the step size at each iteration during the model training process. A well-chosen learning rate is essential for achieving optimal convergence and preventing overshooting or slow convergence in the training phase. Adjusting the learning rate is often necessary to strike a balance between model accuracy and computational efficiency.

n_estimators_: int

The number of model estimators.

Note

All attributes can be accessed using the get_attributes() method.

Note

Several other attributes can be accessed by using the get_vertica_attributes() method.

Examples

The following examples provide a basic understanding of usage. For more detailed examples, please refer to the Machine Learning or the Examples section on the website.

Important

Many tree-based models inherit from the XGB base class, and it’s recommended to use it directly for access to a wider range of options.

Load data for machine learning

We import verticapy:

import verticapy as vp

Hint

By assigning an alias to verticapy, we mitigate the risk of code collisions with other libraries. This precaution is necessary because verticapy uses commonly known function names like “average” and “median”, which can potentially lead to naming conflicts. The use of an alias ensures that the functions from verticapy are used as intended without interfering with functions from other libraries.

For this example, we will use the winequality dataset.

import verticapy.datasets as vpd

data = vpd.load_winequality()
123
fixed_acidity
Numeric(8)
123
volatile_acidity
Numeric(9)
123
citric_acid
Numeric(8)
123
residual_sugar
Numeric(9)
123
chlorides
Float(22)
123
free_sulfur_dioxide
Numeric(9)
123
total_sulfur_dioxide
Numeric(9)
123
density
Float(22)
123
pH
Numeric(8)
123
sulphates
Numeric(8)
123
alcohol
Float(22)
123
quality
Integer
123
good
Integer
Abc
color
Varchar(20)
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Note

VerticaPy offers a wide range of sample datasets that are ideal for training and testing purposes. You can explore the full list of available datasets in the Datasets, which provides detailed information on each dataset and how to use them effectively. These datasets are invaluable resources for honing your data analysis and machine learning skills within the VerticaPy environment.

You can easily divide your dataset into training and testing subsets using the vDataFrame.train_test_split() method. This is a crucial step when preparing your data for machine learning, as it allows you to evaluate the performance of your models accurately.

data = vpd.load_winequality()
train, test = data.train_test_split(test_size = 0.2)

Warning

In this case, VerticaPy utilizes seeded randomization to guarantee the reproducibility of your data split. However, please be aware that this approach may lead to reduced performance. For a more efficient data split, you can use the vDataFrame.to_db() method to save your results into tables or temporary tables. This will help enhance the overall performance of the process.

Model Initialization

First we import the XGBRegressor model:

from verticapy.machine_learning.vertica import XGBRegressor

Then we can create the model:

model = XGBRegressor(
    max_ntree = 3,
    max_depth = 3,
    nbins = 6,
    split_proposal_method = 'global',
    tol = 0.001,
    learning_rate = 0.1,
    min_split_loss = 0,
    weight_reg = 0,
    sample = 0.7,
    col_sample_by_tree = 1,
    col_sample_by_node = 1,
)

Hint

In verticapy 1.0.x and higher, you do not need to specify the model name, as the name is automatically assigned. If you need to re-use the model, you can fetch the model name from the model’s attributes.

Important

The model name is crucial for the model management system and versioning. It’s highly recommended to provide a name if you plan to reuse the model later.

Model Training

We can now fit the model:

model.fit(
    train,
    [
        "fixed_acidity",
        "volatile_acidity",
        "citric_acid",
        "residual_sugar",
        "chlorides",
        "density",
    ],
    "quality",
    test,
)



===========
call_string
===========
xgb_regressor('"public"."_verticapy_tmp_xgbregressor_v_mldb_c97ea83e979811efa8720242ac120002_"', '"public"."_verticapy_tmp_view_v_mldb_c9aca734979811efa8720242ac120002_"', '"quality"', '"fixed_acidity", "volatile_acidity", "citric_acid", "residual_sugar", "chlorides", "density"' USING PARAMETERS exclude_columns='', max_ntree=3, max_depth=3, learning_rate=0.1, min_split_loss=0, weight_reg=0, nbins=6, objective=squarederror, sampling_size=0.7, col_sample_by_tree=1, col_sample_by_node=1)

=======
details
=======
   predictor    |      type      
----------------+----------------
 fixed_acidity  |float or numeric
volatile_acidity|float or numeric
  citric_acid   |float or numeric
 residual_sugar |float or numeric
   chlorides    |float or numeric
    density     |float or numeric


===============
Additional Info
===============
       Name       | Value  
------------------+--------
    tree_count    |   3    
rejected_row_count|   0    
accepted_row_count|  5197  
initial_prediction| 5.80720

Important

To train a model, you can directly use the vDataFrame or the name of the relation stored in the database. The test set is optional and is only used to compute the test metrics. In verticapy, we don’t work using X matrices and y vectors. Instead, we work directly with lists of predictors and the response name.

Features Importance

We can conveniently get the features importance:

result = model.features_importance()

Note

In models such as XGBoost, feature importance is calculated using the average gain of each tree. To determine the final score, VerticaPy sums the scores of each tree, normalizes them and applies an activation function to scale them.

Metrics

We can get the entire report using:

model.report()
value
explained_variance0.0524651482215907
max_error2.81371957335071
median_absolute_error0.686738192254968
mean_absolute_error0.652055475546549
mean_squared_error0.69954468406969
root_mean_squared_error0.836387878959093
r20.0483657007735747
r2_adj0.0439497643502502
aic-450.360750274196
bic-414.332452169739
Rows: 1-10 | Columns: 2

Important

Most metrics are computed using a single SQL query, but some of them might require multiple SQL queries. Selecting only the necessary metrics in the report can help optimize performance. E.g. model.report(metrics = ["mse", "r2"]).

You can utilize the score() function to calculate various regression metrics, with the R-squared being the default.

model.score()
Out[4]: 0.0483657007735747

Prediction

Prediction is straight-forward:

model.predict(
    test,
    [
        "fixed_acidity",
        "volatile_acidity",
        "citric_acid",
        "residual_sugar",
        "chlorides",
        "density",
    ],
    "prediction",
)
123
fixed_acidity
Numeric(8)
123
volatile_acidity
Numeric(9)
123
citric_acid
Numeric(8)
123
residual_sugar
Numeric(9)
123
chlorides
Float(22)
123
free_sulfur_dioxide
Numeric(9)
123
total_sulfur_dioxide
Numeric(9)
123
density
Float(22)
123
pH
Numeric(8)
123
sulphates
Numeric(8)
123
alcohol
Float(22)
123
quality
Integer
123
good
Integer
Abc
color
Varchar(20)
123
prediction
Float(22)
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526.10.210.41.40.06640.5165.00.99123.250.5911.960red5.81371957335071
536.10.240.261.70.03361.0134.00.99033.190.8111.971white5.98412039764347
546.10.240.279.80.06233.0152.00.99663.310.479.560white5.80249641767768
556.10.250.2810.00.05556.0131.00.9943.220.3510.960white5.81371957335071
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576.10.320.286.60.02129.0132.00.991883.150.3611.4571white5.81371957335071
586.10.340.464.70.02921.094.00.9913.290.6212.360white5.81371957335071
596.10.410.1410.40.03718.0119.00.9963.380.4510.050white5.77091973379474
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616.20.190.385.10.01922.082.00.989613.050.3612.560white5.98412039764347
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636.20.230.381.60.04412.0113.00.991763.30.7311.450white5.81371957335071
646.20.270.326.30.04847.0159.00.992823.210.611.060white5.81371957335071
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686.20.350.312.60.03637.092.00.989383.270.5312.871white5.98412039764347
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716.20.560.091.70.05324.032.00.994023.540.611.350red5.72953803181093
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756.30.270.187.70.04845.0186.00.99623.230.479.050white5.80249641767768
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776.30.330.217.90.06636.0161.00.99913.140.518.850white5.77091973379474
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796.31.020.02.00.08317.024.00.994373.590.5511.240red5.72953803181093
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816.40.180.329.60.05224.090.00.99633.350.499.460white5.80249641767768
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846.40.230.391.80.03223.0118.00.99123.320.511.860white5.81371957335071
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866.40.260.496.40.03737.0161.00.99543.380.539.760white5.80249641767768
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886.40.270.324.50.2461.0174.00.99483.120.489.450white5.81371957335071
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1006.50.270.196.60.04598.0175.00.993643.160.3410.160white5.81371957335071
Rows: 1-100 | Columns: 15

Note

Predictions can be made automatically using the test set, in which case you don’t need to specify the predictors. Alternatively, you can pass only the vDataFrame to the predict() function, but in this case, it’s essential that the column names of the vDataFrame match the predictors and response name in the model.

Plots

Tree models can be visualized by drawing their tree plots. For more examples, check out Machine Learning - Tree Plots.

model.plot_tree()
../_images/machine_learning_vertica_xgbreg.png

Note

The above example may not render properly in the doc because of the huge size of the tree. But it should render nicely in jupyter environment.

In order to plot graph using graphviz separately, you can extract the graphviz DOT file code as follows:

model.to_graphviz()
Out[5]: 'digraph Tree {\ngraph [bgcolor="#FFFFFFDD"];\n0 [label="\\"density\\"", shape="box", style="filled", fillcolor="#FFFFFFDD", fontcolor="#000000", color="#000000"]\n0 -> 1 [label="<= 0.990975", color="#000000", fontcolor="#000000"]\n0 -> 2 [label="> 0.990975", color="#000000", fontcolor="#000000"]\n1 [label="\\"volatile_acidity\\"", shape="box", style="filled", fillcolor="#FFFFFFDD", fontcolor="#000000", color="#000000"]\n1 -> 3 [label="<= 0.913333", color="#000000", fontcolor="#000000"]\n1 -> 4 [label="> 0.913333", color="#000000", fontcolor="#000000"]\n2 [label="\\"volatile_acidity\\"", shape="box", style="filled", fillcolor="#FFFFFFDD", fontcolor="#000000", color="#000000"]\n2 -> 5 [label="<= 0.496667", color="#000000", fontcolor="#000000"]\n2 -> 6 [label="> 0.496667", color="#000000", fontcolor="#000000"]\n3 [label="0.646292", fillcolor="#FFFFFFDD", fontcolor="#000000", shape="none", color="#000000"]\n4 [label="-1.807196", fillcolor="#FFFFFFDD", fontcolor="#000000", shape="none", color="#000000"]\n5 [label="-0.008471", fillcolor="#FFFFFFDD", fontcolor="#000000", shape="none", color="#000000"]\n6 [label="-0.464636", fillcolor="#FFFFFFDD", fontcolor="#000000", shape="none", color="#000000"]\n}'

This string can then be copied into a DOT file which can beparsed by graphviz.

Contour plot is another useful plot that can be produced for models with two predictors.

model.contour()

Important

Machine learning models with two predictors can usually benefit from their own contour plot. This visual representation aids in exploring predictions and gaining a deeper understanding of how these models perform in different scenarios. Please refer to Contour Plot for more examples.

Model Register

In order to register the model for tracking and versioning:

model.register("model_v1")

Please refer to /notebooks/ml/model_tracking_versioning/index.ipynb for more details on model tracking and versioning.

Model Exporting

To Memmodel

model.to_memmodel()

Note

MemModel objects serve as in-memory representations of machine learning models. They can be used for both in-database and in-memory prediction tasks. These objects can be pickled in the same way that you would pickle a scikit-learn model.

The preceding methods for exporting the model use MemModel, and it is recommended to use MemModel directly.

To SQL

You can get the SQL query equivalent of the XGB model by:

model.to_sql()
Out[6]: '((CASE WHEN "density" < 0.990975 THEN (CASE WHEN "volatile_acidity" < 0.913333 THEN 0.646292 ELSE -1.807196 END) ELSE (CASE WHEN "volatile_acidity" < 0.496667 THEN -0.008471 ELSE -0.464636 END) END) + (CASE WHEN "density" < 0.99484 THEN (CASE WHEN "density" < 0.990975 THEN 0.553633 ELSE 0.095356 END) ELSE (CASE WHEN "volatile_acidity" < 0.288333 THEN -0.016876 ELSE -0.332643 END) END) + (CASE WHEN "density" < 0.990975 THEN (CASE WHEN "volatile_acidity" < 0.496667 THEN 0.569315 ELSE 0.033093 END) ELSE (CASE WHEN "volatile_acidity" < 0.496667 THEN -0.021654 ELSE -0.407304 END) END)) * 0.1 + 5.80719645949586'

Note

This SQL query can be directly used in any database.

Deploy SQL

To get the SQL query which uses Vertica functions use below:

model.deploySQL()
Out[7]: 'PREDICT_XGB_REGRESSOR("fixed_acidity", "volatile_acidity", "citric_acid", "residual_sugar", "chlorides", "density" USING PARAMETERS model_name = \'"public"."_verticapy_tmp_xgbregressor_v_mldb_c97ea83e979811efa8720242ac120002_"\', match_by_pos = \'true\')'

To Python

To obtain the prediction function in Python syntax, use the following code:

X = [[4.2, 0.17, 0.36, 1.8, 0.029, 0.9899]]

model.to_python()(X)
Out[9]: array([5.98412046])

Hint

The to_python() method is used to retrieve predictions, probabilities, or cluster distances. For specific details on how to use this method for different model types, refer to the relevant documentation for each model.

__init__(name: str = None, overwrite_model: bool = False, max_ntree: int = 10, max_depth: int = 5, nbins: int = 32, split_proposal_method: Literal['local', 'global'] = 'global', tol: float = 0.001, learning_rate: float = 0.1, min_split_loss: float = 0.0, weight_reg: float = 0.0, sample: float = 1.0, col_sample_by_tree: float = 1.0, col_sample_by_node: float = 1.0) → None

Must be overridden in the child class

Methods

__init__([name, overwrite_model, max_ntree, ...])

Must be overridden in the child class

contour([nbins, chart])

Draws the model's contour plot.

deploySQL([X])

Returns the SQL code needed to deploy the model.

does_model_exists(name[, raise_error, ...])

Checks whether the model is stored in the Vertica database.

drop()

Drops the model from the Vertica database.

export_models(name, path[, kind])

Exports machine learning models.

features_importance([tree_id, show, chart])

Computes the model's features importance.

fit(input_relation, X, y[, test_relation, ...])

Trains the model.

get_attributes([attr_name])

Returns the model attributes.

get_match_index(x, col_list[, str_check])

Returns the matching index.

get_params()

Returns the parameters of the model.

get_plotting_lib([class_name, chart, ...])

Returns the first available library (Plotly, Matplotlib, or Highcharts) to draw a specific graphic.

get_score([tree_id])

Returns the feature importance metrics for the input tree.

get_tree([tree_id])

Returns a table with all the input tree information.

get_vertica_attributes([attr_name])

Returns the model Vertica attributes.

import_models(path[, schema, kind])

Imports machine learning models.

plot([max_nb_points, chart])

Draws the model.

plot_tree([tree_id, pic_path])

Draws the input tree.

predict(vdf[, X, name, inplace])

Predicts using the input relation.

register(registered_name[, raise_error])

Registers the model and adds it to in-DB Model versioning environment with a status of 'under_review'.

regression_report([metrics])

Computes a regression report

report([metrics])

Computes a regression report

score([metric])

Computes the model score.

set_params([parameters])

Sets the parameters of the model.

summarize()

Summarizes the model.

to_binary(path)

Exports the model to the Vertica Binary format.

to_graphviz([tree_id, classes_color, ...])

Returns the code for a Graphviz tree.

to_json([path])

Creates a Python XGBoost JSON file

to_memmodel()

Converts the model to an InMemory object that can be used for different types of predictions.

to_pmml(path)

Exports the model to PMML.

to_python([return_proba, ...])

Returns the Python function needed for in-memory scoring without using built-in Vertica functions.

to_sql([X, return_proba, ...])

Returns the SQL code needed to deploy the model without using built-in Vertica functions.

to_tf(path)

Exports the model to the Frozen Graph format (TensorFlow).

Attributes