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verticapy.machine_learning.model_selection.hp_tuning.bayesian_search_cv

verticapy.machine_learning.model_selection.hp_tuning.bayesian_search_cv(estimator: VerticaModel, input_relation: Annotated[str | vDataFrame, ''], X: Annotated[str | list[str], 'STRING representing one column or a list of columns'], y: str, metric: str = 'auto', cv: int = 3, pos_label: Annotated[bool | float | str | timedelta | datetime, 'Python Scalar'] | None = None, cutoff: float = -1, param_grid: None | dict | list = None, random_nbins: int = 16, bayesian_nbins: int | None = None, random_grid: bool = False, lmax: int = 15, nrows: int = 100000, k_tops: int = 10, RFmodel_params: dict | None = None, print_info: bool = True, **kwargs) TableSample

Computes the k-fold bayesian search of an estimator using a random forest model to estimate a probably optimal set of parameters.

estimator: object

Vertica estimator with a fit method.

input_relation: SQLRelation

Relation used to train the model.

X: SQLColumns

list of the predictor columns.

y: str

Response Column.

metric: str, optional

Metric used for the model evaluation.

  • auto:

    logloss for classification & RMSE for regression.

For Classification

  • accuracy:

    Accuracy.

    \[Accuracy = \frac{TP + TN}{TP + TN + FP + FN}\]
  • auc:

    Area Under the Curve (ROC).

    \[AUC = \int_{0}^{1} TPR(FPR) \, dFPR\]
  • ba:

    Balanced Accuracy.

    \[BA = \frac{TPR + TNR}{2}\]
  • bm:

    Informedness

    \[BM = TPR + TNR - 1\]
  • csi:

    Critical Success Index

    \[index = \frac{TP}{TP + FN + FP}\]
  • f1:

    F1 Score .. math:

    F_1 Score = 2 \times 
    

rac{Precision times Recall}{Precision + Recall}

  • fdr:

    False Discovery Rate

    \[FDR = 1 - PPV\]
  • fm:

    Fowlkes-Mallows index

    \[FM = \sqrt{PPV * TPR}\]
  • fnr:

    False Negative Rate

    \[FNR = \frac{FN}{FN + TP}\]
  • for:

    False Omission Rate

    \[FOR = 1 - NPV\]
  • fpr:

    False Positive Rate

    \[FPR = \frac{FP}{FP + TN}\]
  • logloss:

    Log Loss

    \[Loss = -\frac{1}{N} \sum_{i=1}^{N} \left( y_i \log(p_i) + (1 - y_i) \log(1 - p_i) \right)\]
  • lr+:

    Positive Likelihood Ratio.

    \[LR+ = \frac{TPR}{FPR}\]
  • lr-:

    Negative Likelihood Ratio.

    \[LR- = \frac{FNR}{TNR}\]
  • dor:

    Diagnostic Odds Ratio.

    \[DOR = \frac{TP \times TN}{FP \times FN}\]
  • mcc:

    Matthews Correlation Coefficient

  • mk:

    Markedness

    \[MK = PPV + NPV - 1\]
  • npv:

    Negative Predictive Value

    \[NPV = \frac{TN}{TN + FN}\]
  • prc_auc:

    Area Under the Curve (PRC)

    \[AUC = \int_{0}^{1} Precision(Recall) \, dRecall\]
  • precision:

    Precision

    \[TP / (TP + FP)\]
  • pt:

    Prevalence Threshold.

    \[\frac{\sqrt{FPR}}{\sqrt{TPR} + \sqrt{FPR}}\]
  • recall:

    Recall.

    \[TP / (TP + FN)\]
  • specificity:

    Specificity.

    \[TN / (TN + FP)\]

For Regression

  • max:

    Max Error.

    \[ME = \max_{i=1}^{n} \left| y_i - \hat{y}_i \right|\]
  • mae:

    Mean Absolute Error.

    \[MAE = \frac{1}{n} \sum_{i=1}^{n} \left| y_i - \hat{y}_i \right|\]
  • median:

    Median Absolute Error.

    \[MedAE = \text{median}_{i=1}^{n} \left| y_i - \hat{y}_i \right|\]
  • mse:

    Mean Squared Error.

    \[MSE = \frac{1}{n} \sum_{i=1}^{n} \left( y_i - \hat{y}_i \right)^2\]
  • msle:

    Mean Squared Log Error.

    \[MSLE = \frac{1}{n} \sum_{i=1}^{n} (\log(1 + y_i) - \log(1 + \hat{y}_i))^2\]
  • r2:

    R squared coefficient.

    \[R^2 = 1 - \frac{\sum_{i=1}^{n} (y_i - \hat{y}_i)^2}{\sum_{i=1}^{n} (y_i - \bar{y})^2}\]
  • r2a:

    R2 adjusted

    \[\text{Adjusted } R^2 = 1 - \frac{(1 - R^2)(n - 1)}{n - k - 1}\]
  • var:

    Explained Variance.

    \[VAR = 1 - \frac{Var(y - \hat{y})}{Var(y)}\]
  • rmse:

    Root-mean-squared error

    \[RMSE = \sqrt{\frac{1}{n} \sum_{i=1}^{n} (y_i - \hat{y}_i)^2}\]
cv: int, optional

Number of folds.

pos_label: PythonScalar, optional

The main class to be considered as positive (classification only).

cutoff: float, optional

The model cutoff (classification only).

param_grid: dict | list, optional

Dictionary of the parameters to test. It can also be a list of the different combinations. If empty, a parameter grid is generated.

random_nbins: int, optional

Number of bins used to compute the different parameters categories in the random parameters generation.

bayesian_nbins: int, optional

Number of bins used to compute the different parameters categories in the bayesian table generation.

random_grid: bool, optional

If True, the rows used to find the optimal function are used randomnly. Otherwise, they are regularly spaced.

lmax: int, optional

Maximum length of each parameter list.

nrows: int, optional

Number of rows to use when performing the bayesian search.

k_tops: int, optional

When performing the bayesian search, the final stage is to retrain the top possible combinations. ‘k_tops’ represents the number of models to train at this stage in order to find the most efficient model.

RFmodel_params: dict, optional

dictionary of the random forest model parameters used to estimate a probably optimal set of parameters.

print_info: bool, optional

If True, prints the model information at each step.

TableSample

result of the bayesian search.

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 Wine Quality 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.

Next, we can initialize a LogisticRegression model:

from verticapy.machine_learning.vertica import LogisticRegression

model = LogisticRegression()

Now we can conveniently use the bayesian_search_cv() function to find an optimal set of parameters estimator.

from verticapy.machine_learning.model_selection import bayesian_search_cv

result = bayesian_search_cv(
    model,
    input_relation = data,
    X = [
        "fixed_acidity",
        "volatile_acidity",
        "citric_acid",
        "residual_sugar",
        "chlorides",
        "density",
    ],
    y = "good",
    cv = 3,
)
avg_score
avg_train_score
avg_time
score_std
score_train_std
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Rows: 1-25 | Columns: 6

Note

In VerticaPy, Bayesian optimization utilizes the RandomForest model instead of Gaussian processes. The optimization process involves iteratively selecting and evaluating sets of parameters, with the RandomForest model predicting the performance of different parameter configurations. This approach allows VerticaPy to efficiently navigate the parameter space and identify optimal settings for machine learning models, enhancing their overall performance.

See also

grid_search_cv() : Computes the k-fold grid search of an estimator.
randomized_search_cv() : Computes the K-Fold randomized search of an estimator.