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verticapy.machine_learning.vertica.svm.LinearSVC#

class verticapy.machine_learning.vertica.svm.LinearSVC(name: str = None, overwrite_model: bool = False, tol: float = 0.0001, C: float = 1.0, intercept_scaling: float = 1.0, intercept_mode: Literal['regularized', 'unregularized'] = 'regularized', class_weight: Literal['auto', 'none'] | list = [1, 1], max_iter: int = 100)#

Creates a LinearSVC object using the Vertica Support Vector Machine (SVM) algorithm on the data. Given a set of training examples, where each is marked as belonging to one of two categories, an SVM training algorithm builds a model that assigns new examples to one category or the other, making it a non-probabilistic binary linear classifier.

Parameters#

name: str, optional

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

overwrite_model: bool, optional

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

tol: float, optional

Tolerance for stopping criteria. This is used to control accuracy.

C: float, optional

Weight for misclassification cost. The algorithm minimizes the regularization cost and the misclassification cost.

intercept_scaling: float

A float value, serves as the value of a dummy feature whose coefficient Vertica uses to calculate the model intercept. Because the dummy feature is not in the training data, its values are set to a constant, by default set to 1.

intercept_mode: str, optional

Specify how to treat the intercept.

  • regularized:

    Fits the intercept and applies a regularization.

  • unregularized:

    Fits the intercept but does not include it in regularization.

class_weight: str | list, optional

Specifies how to determine weights for the two classes. It can be a list of 2 elements or one of the following methods:

  • auto:

    Weights each class according to the number of samples.

  • none:

    No weights are used.

max_iter: int, optional

The maximum number of iterations that the algorithm performs.

Attributes#

Many attributes are created during the fitting phase.

coef_: numpy.array

The regression coefficients. The order of coefficients is the same as the order of columns used during the fitting phase.

intercept_: float

The expected value of the dependent variable when all independent variables are zero, serving as the baseline or constant term in the model.

features_importance_: numpy.array

The importance of features is computed through the model coefficients, which are normalized based on their range. Subsequently, an activation function calculates the final score. It is necessary to use the features_importance() method to compute it initially, and the computed values will be subsequently utilized for subsequent calls.

classes_: numpy.array

The classes labels.

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.

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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Rows: 1-100 | Columns: 14

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 LinearSVC model:

from verticapy.machine_learning.vertica import LinearSVC

Then we can create the model:

model = LinearSVC(
    tol = 1e-4,
    C = 1.0,
    intercept_scaling = 1.0,
    intercept_mode = "regularized",
    class_weight = [1, 1],
    max_iter = 100,
)

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"
    ],
    "good",
    test,
)

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

For LinearModel, feature importance is computed using the coefficients. These coefficients are then normalized using the feature distribution. An activation function is applied to get the final score.

Metrics#

We can get the entire report using:

model.report()
value
auc0.6634095201510934
prc_auc0.24623754546890747
accuracy0.8202764976958525
log_loss0.231043032730828
precision0.0
recall0.0
f1_score0.0
mcc0.0
informedness0.0
markedness-0.17972350230414746
csi0.0
Rows: 1-11 | 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 = ["auc", "accuracy"]).

For classification models, we can easily modify the cutoff to observe the effect on different metrics:

model.report(cutoff = 0.2)
value
auc0.6634095201510934
prc_auc0.24623754546890747
accuracy0.19047619047619047
log_loss0.231043032730828
precision0.18167701863354038
recall1.0
f1_score0.3074901445466492
mcc0.048800962614738055
informedness0.013108614232209659
markedness0.18167701863354035
csi0.18167701863354038
Rows: 1-11 | Columns: 2

You can also use the LinearModel.score function to compute any classification metric. The default metric is the accuracy:

model.score()
Out[3]: 0.8202764976958525

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
Integer
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1005.80.320.384.750.03323.094.00.9913.420.4211.871white0
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.

Probabilities#

It is also easy to get the model’s probabilities:

model.predict_proba(
    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
Integer
123
prediction_0
Float(22)
123
prediction_1
Float(22)
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Rows: 1-100 | Columns: 17

Note

Probabilities are added to the vDataFrame, and VerticaPy uses the corresponding probability function in SQL behind the scenes. You can use the pos_label parameter to add only the probability of the selected category.

Confusion Matrix#

You can obtain the confusion matrix of your choice by specifying the desired cutoff.

model.confusion_matrix(cutoff = 0.5)
Out[4]: 
array([[1068,    0],
       [ 234,    0]])

Note

In classification, the cutoff is a threshold value used to determine class assignment based on predicted probabilities or scores from a classification model. In binary classification, if the predicted probability for a specific class is greater than or equal to the cutoff, the instance is assigned to the positive class; otherwise, it is assigned to the negative class. Adjusting the cutoff allows for trade-offs between true positives and false positives, enabling the model to be optimized for specific objectives or to consider the relative costs of different classification errors. The choice of cutoff is critical for tailoring the model’s performance to meet specific needs.

Main Plots (Classification Curves)#

Classification models allow for the creation of various plots that are very helpful in understanding the model, such as the ROC Curve, PRC Curve, Cutoff Curve, Gain Curve, and more.

Most of the classification curves can be found in the Machine Learning - Classification Curve.

For example, let’s draw the model’s ROC curve.

model.roc_curve()

Important

Most of the curves have a parameter called nbins, which is essential for estimating metrics. The larger the nbins, the more precise the estimation, but it can significantly impact performance. Exercise caution when increasing this parameter excessively.

Hint

In binary classification, various curves can be easily plotted. However, in multi-class classification, it’s important to select the pos_label, representing the class to be treated as positive when drawing the curve.

Other Plots#

If the model allows, you can also generate relevant plots. For example, classification plots can be found in the Machine Learning - Classification Plots.

model.plot()

Important

The plotting feature is typically suitable for models with fewer than three predictors.

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.

Parameter Modification#

In order to see the parameters:

model.get_params()
Out[5]: 
{'tol': 0.0001,
 'C': 1.0,
 'intercept_scaling': 1.0,
 'intercept_mode': 'regularized',
 'class_weight': [1, 1],
 'max_iter': 100}

And to manually change some of the parameters:

model.set_params({'tol': 0.001})

Model Register#

In order to register the model for tracking and versioning:

model.register("model_v1")

Please refer to Model Tracking and Versioning 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 following methods for exporting the model use MemModel, and it is recommended to use MemModel directly.

To SQL

You can get the SQL code by:

model.to_sql()
Out[7]: '((1 / (1 + EXP(- (1.47377673486566 + 0.00527762759337545 * "fixed_acidity" + -0.543583271863033 * "volatile_acidity" + 0.192258472232652 * "citric_acid" + -0.0201778588607175 * "residual_sugar" + -4.56718403612728 * "chlorides" + -1.63874906986082 * "density")))) > 0.5)::int'

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([0])

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, tol: float = 0.0001, C: float = 1.0, intercept_scaling: float = 1.0, intercept_mode: Literal['regularized', 'unregularized'] = 'regularized', class_weight: Literal['auto', 'none'] | list = [1, 1], max_iter: int = 100) None#

Methods

__init__([name, overwrite_model, tol, C, ...])

classification_report([metrics, cutoff, nbins])

Computes a classification report using multiple model evaluation metrics (auc, accuracy, f1...).

confusion_matrix([cutoff])

Computes the model confusion matrix.

contour([nbins, chart])

Draws the model's contour plot.

cutoff_curve([nbins, show, chart])

Draws the model Cutoff curve.

deploySQL([X, cutoff])

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([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_vertica_attributes([attr_name])

Returns the model Vertica attributes.

import_models(path[, schema, kind])

Imports machine learning models.

lift_chart([nbins, show, chart])

Draws the model Lift Chart.

plot([max_nb_points, chart])

Draws the model.

prc_curve([nbins, show, chart])

Draws the model PRC curve.

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

Makes predictions on the input relation.

predict_proba(vdf[, X, name, pos_label, inplace])

Returns the model's probabilities 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'.

report([metrics, cutoff, nbins])

Computes a classification report using multiple model evaluation metrics (auc, accuracy, f1...).

roc_curve([nbins, show, chart])

Draws the model ROC curve.

score([metric, cutoff, nbins])

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_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