verticapy.machine_learning.vertica.cluster.NearestCentroid¶

class verticapy.machine_learning.vertica.cluster.NearestCentroid(name: str = None, overwrite_model: bool = False, p: int = 2)¶

Creates a NearestCentroid object using the k-nearest centroid algorithm. This object uses pure SQL to compute the distances and final score.

Important

This algorithm is not Vertica Native and relies solely on SQL for attribute computation. While this model does not take advantage of the benefits provided by a model management system, including versioning and tracking, the SQL code it generates can still be used to create a pipeline.

Parameters¶

p: int, optional: The p corresponding to the one of the p-distances (distance metric used to compute the model).

Attributes¶

Many attributes are created during the fitting phase.

clusters_: numpy.array: Cluster centers.
p_: int: The p of the p-distances.
classes_: numpy.array: The classes labels.

Note

All attributes can be accessed using the get_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 iris dataset.

import verticapy.datasets as vpd

data = vpd.load_iris()

	123 SepalLengthCm Numeric(7)	123 SepalWidthCm Numeric(7)	123 PetalLengthCm Numeric(7)	123 PetalWidthCm Numeric(7)	Abc Species Varchar(30)
1	3.3	4.5	5.6	7.8	Iris-setosa
2	3.3	4.5	5.6	7.8	Iris-setosa
3	3.3	4.5	5.6	7.8	Iris-setosa
4	3.3	4.5	5.6	7.8	Iris-setosa
5	3.3	4.5	5.6	7.8	Iris-setosa
6	3.3	4.5	5.6	7.8	Iris-setosa
7	3.3	4.5	5.6	7.8	Iris-setosa
8	3.3	4.5	5.6	7.8	Iris-setosa
9	3.3	4.5	5.6	7.8	Iris-setosa
10	3.3	4.5	5.6	7.8	Iris-setosa
11	3.3	4.5	5.6	7.8	Iris-setosa
12	3.3	4.5	5.6	7.8	Iris-setosa
13	3.3	4.5	5.6	7.8	Iris-setosa
14	3.3	4.5	5.6	7.8	Iris-setosa
15	3.3	4.5	5.6	7.8	Iris-setosa
16	3.3	4.5	5.6	7.8	Iris-setosa
17	3.3	4.5	5.6	7.8	Iris-setosa
18	3.3	4.5	5.6	7.8	Iris-setosa
19	3.3	4.5	5.6	7.8	Iris-setosa
20	3.3	4.5	5.6	7.8	Iris-setosa
21	3.3	4.5	5.6	7.8	Iris-setosa
22	3.3	4.5	5.6	7.8	Iris-setosa
23	3.3	4.5	5.6	7.8	Iris-setosa
24	3.3	4.5	5.6	7.8	Iris-setosa
25	3.3	4.5	5.6	7.8	Iris-setosa
26	3.3	4.5	5.6	7.8	Iris-setosa
27	4.3	3.0	1.1	0.1	Iris-setosa
28	4.3	4.7	9.6	1.8	Iris-virginica
29	4.3	4.7	9.6	1.8	Iris-virginica
30	4.3	4.7	9.6	1.8	Iris-virginica
31	4.3	4.7	9.6	1.8	Iris-virginica
32	4.3	4.7	9.6	1.8	Iris-virginica
33	4.3	4.7	9.6	1.8	Iris-virginica
34	4.3	4.7	9.6	1.8	Iris-virginica
35	4.3	4.7	9.6	1.8	Iris-virginica
36	4.3	4.7	9.6	1.8	Iris-virginica
37	4.3	4.7	9.6	1.8	Iris-virginica
38	4.3	4.7	9.6	1.8	Iris-virginica
39	4.3	4.7	9.6	1.8	Iris-virginica
40	4.3	4.7	9.6	1.8	Iris-virginica
41	4.3	4.7	9.6	1.8	Iris-virginica
42	4.3	4.7	9.6	1.8	Iris-virginica
43	4.3	4.7	9.6	1.8	Iris-virginica
44	4.3	4.7	9.6	1.8	Iris-virginica
45	4.3	4.7	9.6	1.8	Iris-virginica
46	4.3	4.7	9.6	1.8	Iris-virginica
47	4.3	4.7	9.6	1.8	Iris-virginica
48	4.3	4.7	9.6	1.8	Iris-virginica
49	4.3	4.7	9.6	1.8	Iris-virginica
50	4.3	4.7	9.6	1.8	Iris-virginica
51	4.3	4.7	9.6	1.8	Iris-virginica
52	4.3	4.7	9.6	1.8	Iris-virginica
53	4.3	4.7	9.6	1.8	Iris-virginica
54	4.4	2.9	1.4	0.2	Iris-setosa
55	4.4	3.0	1.3	0.2	Iris-setosa
56	4.4	3.2	1.3	0.2	Iris-setosa
57	4.5	2.3	1.3	0.3	Iris-setosa
58	4.6	3.1	1.5	0.2	Iris-setosa
59	4.6	3.2	1.4	0.2	Iris-setosa
60	4.6	3.4	1.4	0.3	Iris-setosa
61	4.6	3.6	1.0	0.2	Iris-setosa
62	4.7	3.2	1.3	0.2	Iris-setosa
63	4.7	3.2	1.6	0.2	Iris-setosa
64	4.8	3.0	1.4	0.1	Iris-setosa
65	4.8	3.0	1.4	0.3	Iris-setosa
66	4.8	3.1	1.6	0.2	Iris-setosa
67	4.8	3.4	1.6	0.2	Iris-setosa
68	4.8	3.4	1.9	0.2	Iris-setosa
69	4.9	2.4	3.3	1.0	Iris-versicolor
70	4.9	2.5	4.5	1.7	Iris-virginica
71	4.9	3.0	1.4	0.2	Iris-setosa
72	4.9	3.1	1.5	0.1	Iris-setosa
73	4.9	3.1	1.5	0.1	Iris-setosa
74	4.9	3.1	1.5	0.1	Iris-setosa
75	5.0	2.0	3.5	1.0	Iris-versicolor
76	5.0	2.3	3.3	1.0	Iris-versicolor
77	5.0	3.0	1.6	0.2	Iris-setosa
78	5.0	3.2	1.2	0.2	Iris-setosa
79	5.0	3.3	1.4	0.2	Iris-setosa
80	5.0	3.4	1.5	0.2	Iris-setosa
81	5.0	3.4	1.6	0.4	Iris-setosa
82	5.0	3.5	1.3	0.3	Iris-setosa
83	5.0	3.5	1.6	0.6	Iris-setosa
84	5.0	3.6	1.4	0.2	Iris-setosa
85	5.1	2.5	3.0	1.1	Iris-versicolor
86	5.1	3.3	1.7	0.5	Iris-setosa
87	5.1	3.4	1.5	0.2	Iris-setosa
88	5.1	3.5	1.4	0.2	Iris-setosa
89	5.1	3.5	1.4	0.3	Iris-setosa
90	5.1	3.7	1.5	0.4	Iris-setosa
91	5.1	3.8	1.5	0.3	Iris-setosa
92	5.1	3.8	1.6	0.2	Iris-setosa
93	5.1	3.8	1.9	0.4	Iris-setosa
94	5.2	2.7	3.9	1.4	Iris-versicolor
95	5.2	3.4	1.4	0.2	Iris-setosa
96	5.2	3.5	1.5	0.2	Iris-setosa
97	5.2	4.1	1.5	0.1	Iris-setosa
98	5.3	3.7	1.5	0.2	Iris-setosa
99	5.4	3.0	4.5	1.5	Iris-versicolor
100	5.4	3.4	1.5	0.4	Iris-setosa

Rows: 1-100 | Columns: 5

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_iris()
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.

Balancing the Dataset¶

In VerticaPy, balancing a dataset to address class imbalances is made straightforward through the balance() function within the preprocessing module. This function enables users to rectify skewed class distributions efficiently. By specifying the target variable and setting parameters like the method for balancing, users can effortlessly achieve a more equitable representation of classes in their dataset. Whether opting for over-sampling, under-sampling, or a combination of both, VerticaPy’s balance() function streamlines the process, empowering users to enhance the performance and fairness of their machine learning models trained on imbalanced data.

To balance the dataset, use the following syntax.

from verticapy.machine_learning.vertica.preprocessing import balance

balanced_train = balance(
    name = "my_schema.train_balanced",
    input_relation = train,
    y = "good",
    method = "hybrid",
)

Note

With this code, a table named train_balanced is created in the my_schema schema. It can then be used to train the model. In the rest of the example, we will work with the full dataset.

Hint

Balancing the dataset is a crucial step in improving the accuracy of machine learning models, particularly when faced with imbalanced class distributions. By addressing disparities in the number of instances across different classes, the model becomes more adept at learning patterns from all classes rather than being biased towards the majority class. This, in turn, enhances the model’s ability to make accurate predictions for under-represented classes. The balanced dataset ensures that the model is not dominated by the majority class and, as a result, leads to more robust and unbiased model performance. Therefore, by employing techniques such as over-sampling, under-sampling, or a combination of both during dataset preparation, practitioners can significantly contribute to achieving higher accuracy and better generalization of their machine learning models.

Model Initialization¶

First we import the NearestCentroid model:

from verticapy.machine_learning.vertica import NearestCentroid

Then we can create the model:

model = NearestCentroid(p = 2)

Model Training¶

We can now fit the model:

model.fit(
    train,
    [
        "SepalLengthCm",
        "SepalWidthCm",
        "PetalLengthCm",
        "PetalWidthCm",
    ],
    "Species",
    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.

Important

As this model is not native, it solely relies on SQL statements to compute various attributes, storing them within the object. No data is saved in the database.

Metrics¶

We can get the entire report using:

model.report()

	Iris-setosa	Iris-versicolor	Iris-virginica	avg_macro	avg_weighted	avg_micro
auc	1.0	1.0	0.9017094017094016	0.9672364672364672	0.9597902097902097	[null]
prc_auc	1.0	0.9999999999999998	0.9008978239956499	0.9669659413318832	0.9594582007254931	[null]
accuracy	0.7727272727272727	0.5909090909090909	0.8181818181818182	0.7272727272727274	0.7541322314049587	0.7272727272727273
log_loss	0.219410015811111	0.184883532269521	0.224385522885376	0.20955969032200264	0.21438321525343965	[null]
precision	1.0	0.3333333333333333	1.0	0.7777777777777777	0.8636363636363636	0.5909090909090909
recall	0.4117647058823529	1.0	0.5555555555555556	0.6557734204793028	0.5909090909090909	0.5909090909090909
f1_score	0.5833333333333334	0.5	0.7142857142857143	0.5992063492063493	0.6198593073593074	0.5909090909090909
mcc	0.5481577761336338	0.40237390808147827	0.651794907395869	0.5341088638703271	0.5607353568211528	0.38636363636363635
informedness	0.4117647058823528	0.48571428571428577	0.5555555555555556	0.4843448490507314	0.4857142857142857	0.38636363636363624
markedness	0.7297297297297298	0.33333333333333326	0.7647058823529411	0.6092563151386681	0.6629570747217806	0.38636363636363624
csi	0.4117647058823529	0.3333333333333333	0.5555555555555556	0.4335511982570806	0.45454545454545453	0.41935483870967744

Rows: 1-11 | Columns: 7

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)

	Iris-setosa	Iris-versicolor	Iris-virginica	avg_macro	avg_weighted	avg_micro
auc	1.0	1.0	0.9017094017094016	0.9672364672364672	0.9597902097902097	[null]
prc_auc	1.0	0.9999999999999998	0.9008978239956499	0.9669659413318832	0.9594582007254931	[null]
accuracy	0.7045454545454546	0.20454545454545456	0.5909090909090909	0.5	0.5557851239669422	0.5
log_loss	0.219410015811111	0.184883532269521	0.224385522885376	0.20955969032200264	0.21438321525343965	[null]
precision	0.5666666666666667	0.20454545454545456	0.5	0.42373737373737375	0.46532369146005514	0.4
recall	1.0	1.0	1.0	1.0	1.0	1.0
f1_score	0.7234042553191489	0.339622641509434	0.6666666666666666	0.576564521165083	0.6216926389547827	0.5714285714285715
mcc	0.5420582630066875	0.0	0.3922322702763681	0.3114301777610185	0.36989025763837075	0.31622776601683794
informedness	0.5185185185185186	0.0	0.3076923076923077	0.2754036087369421	0.32621082621082625	0.25
markedness	0.5666666666666667	-0.7954545454545454	0.5	0.09040404040404042	0.26077823691460056	0.3999999999999999
csi	0.5666666666666667	0.20454545454545456	0.5	0.42373737373737375	0.46532369146005514	0.4

Rows: 1-11 | Columns: 7

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

model.score(metric = "f1", average = "macro")
Out[4]: 0.5992063492063493

Note

For multi-class scoring, verticapy allows the flexibility to use three averaging techniques: micro, macro and weighted. Please refer to this link for more details on how they are calculated.

Prediction¶

Prediction is straight-forward:

model.predict(
    test,
    [
        "SepalLengthCm",
        "SepalWidthCm",
        "PetalLengthCm",
        "PetalWidthCm",
    ],
    "prediction",
)

	123 SepalLengthCm Numeric(7)	123 SepalWidthCm Numeric(7)	123 PetalLengthCm Numeric(7)	123 PetalWidthCm Numeric(7)	Abc Species Varchar(30)	Abc prediction Varchar(15)
1	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa
2	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa
3	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa
4	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa
5	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa
6	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa
7	4.3	3.0	1.1	0.1	Iris-setosa	Iris-versicolor
8	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica
9	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica
10	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica
11	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica
12	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica
13	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica
14	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica
15	4.4	3.2	1.3	0.2	Iris-setosa	Iris-versicolor
16	4.8	3.1	1.6	0.2	Iris-setosa	Iris-versicolor
17	4.8	3.4	1.9	0.2	Iris-setosa	Iris-versicolor
18	4.9	2.5	4.5	1.7	Iris-virginica	Iris-versicolor
19	4.9	3.1	1.5	0.1	Iris-setosa	Iris-versicolor
20	4.9	3.1	1.5	0.1	Iris-setosa	Iris-versicolor
21	5.0	3.2	1.2	0.2	Iris-setosa	Iris-versicolor
22	5.0	3.6	1.4	0.2	Iris-setosa	Iris-versicolor
23	5.4	3.4	1.5	0.4	Iris-setosa	Iris-versicolor
24	5.4	3.4	1.7	0.2	Iris-setosa	Iris-versicolor
25	5.5	2.3	4.0	1.3	Iris-versicolor	Iris-versicolor
26	5.6	3.0	4.5	1.5	Iris-versicolor	Iris-versicolor
27	5.7	3.0	4.2	1.2	Iris-versicolor	Iris-versicolor
28	5.8	2.6	4.0	1.2	Iris-versicolor	Iris-versicolor
29	5.8	2.7	4.1	1.0	Iris-versicolor	Iris-versicolor
30	5.8	2.7	5.1	1.9	Iris-virginica	Iris-versicolor
31	5.8	2.8	5.1	2.4	Iris-virginica	Iris-versicolor
32	5.9	3.0	4.2	1.5	Iris-versicolor	Iris-versicolor
33	6.3	2.3	4.4	1.3	Iris-versicolor	Iris-versicolor
34	6.4	2.7	5.3	1.9	Iris-virginica	Iris-versicolor
35	6.4	2.8	5.6	2.2	Iris-virginica	Iris-versicolor
36	6.6	3.0	4.4	1.4	Iris-versicolor	Iris-versicolor
37	6.7	3.1	4.7	1.5	Iris-versicolor	Iris-versicolor
38	6.9	3.1	5.1	2.3	Iris-virginica	Iris-versicolor
39	6.9	3.1	5.4	2.1	Iris-virginica	Iris-versicolor
40	7.2	3.0	5.8	1.6	Iris-virginica	Iris-versicolor
41	7.7	2.8	6.7	2.0	Iris-virginica	Iris-virginica
42	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa
43	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica
44	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica

Rows: 1-44 | Columns: 6

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,
    [
        "SepalLengthCm",
        "SepalWidthCm",
        "PetalLengthCm",
        "PetalWidthCm",
    ],
    "prediction",
)

	123 SepalLengthCm Numeric(7)	123 SepalWidthCm Numeric(7)	123 PetalLengthCm Numeric(7)	123 PetalWidthCm Numeric(7)	Abc Species Varchar(30)	Abc prediction Varchar(15)	123 prediction_irissetosa Float(22)	123 prediction_irisversicolor Float(22)	123 prediction_irisvirginica Float(22)
1	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa	0.396381814771746	0.285670531542205	0.317947653686049
2	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa	0.396381814771746	0.285670531542205	0.317947653686049
3	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa	0.396381814771746	0.285670531542205	0.317947653686049
4	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa	0.396381814771746	0.285670531542205	0.317947653686049
5	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa	0.396381814771746	0.285670531542205	0.317947653686049
6	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa	0.396381814771746	0.285670531542205	0.317947653686049
7	4.3	3.0	1.1	0.1	Iris-setosa	Iris-versicolor	0.379734552842337	0.392357174613991	0.227908272543672
8	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica	0.232107095005353	0.26197205744578	0.505920847548867
9	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica	0.232107095005353	0.26197205744578	0.505920847548867
10	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica	0.232107095005353	0.26197205744578	0.505920847548867
11	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica	0.232107095005353	0.26197205744578	0.505920847548867
12	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica	0.232107095005353	0.26197205744578	0.505920847548867
13	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica	0.232107095005353	0.26197205744578	0.505920847548867
14	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica	0.232107095005353	0.26197205744578	0.505920847548867
15	4.4	3.2	1.3	0.2	Iris-setosa	Iris-versicolor	0.381239549318794	0.394511434935913	0.224249015745294
16	4.8	3.1	1.6	0.2	Iris-setosa	Iris-versicolor	0.363049183789877	0.416327247839306	0.220623568370818
17	4.8	3.4	1.9	0.2	Iris-setosa	Iris-versicolor	0.360198343948455	0.420250217088923	0.219551438962622
18	4.9	2.5	4.5	1.7	Iris-virginica	Iris-versicolor	0.243327746800057	0.546051124367299	0.210621128832644
19	4.9	3.1	1.5	0.1	Iris-setosa	Iris-versicolor	0.359646672601595	0.41712926843067	0.223224058967735
20	4.9	3.1	1.5	0.1	Iris-setosa	Iris-versicolor	0.359646672601595	0.41712926843067	0.223224058967735
21	5.0	3.2	1.2	0.2	Iris-setosa	Iris-versicolor	0.368852111557597	0.407478131317743	0.22366975712466
22	5.0	3.6	1.4	0.2	Iris-setosa	Iris-versicolor	0.371083036951049	0.40549644246018	0.223420520588772
23	5.4	3.4	1.5	0.4	Iris-setosa	Iris-versicolor	0.360971742279516	0.4208857574975	0.218142500222984
24	5.4	3.4	1.7	0.2	Iris-setosa	Iris-versicolor	0.348280629938078	0.43125651049698	0.220462859564941
25	5.5	2.3	4.0	1.3	Iris-versicolor	Iris-versicolor	0.162748807304786	0.699133529903945	0.138117662791268
26	5.6	3.0	4.5	1.5	Iris-versicolor	Iris-versicolor	0.13350854171098	0.732517805689522	0.133973652599498
27	5.7	3.0	4.2	1.2	Iris-versicolor	Iris-versicolor	0.0992448362719544	0.808275976718031	0.0924791870100147
28	5.8	2.6	4.0	1.2	Iris-versicolor	Iris-versicolor	0.0968252431540244	0.817072234848162	0.0861025219978133
29	5.8	2.7	4.1	1.0	Iris-versicolor	Iris-versicolor	0.100232730577828	0.804633028055739	0.095134241366433
30	5.8	2.7	5.1	1.9	Iris-virginica	Iris-versicolor	0.186898988942092	0.555378996580417	0.257722014477492
31	5.8	2.8	5.1	2.4	Iris-virginica	Iris-versicolor	0.230829918559465	0.475955724734366	0.29321435670617
32	5.9	3.0	4.2	1.5	Iris-versicolor	Iris-versicolor	0.0890103608466354	0.829609778096014	0.0813798610573502
33	6.3	2.3	4.4	1.3	Iris-versicolor	Iris-versicolor	0.129936325799823	0.727017375062842	0.143046299137335
34	6.4	2.7	5.3	1.9	Iris-virginica	Iris-versicolor	0.186242417652747	0.508887418013017	0.304870164334236
35	6.4	2.8	5.6	2.2	Iris-virginica	Iris-versicolor	0.198223993603442	0.422990674155991	0.378785332240567
36	6.6	3.0	4.4	1.4	Iris-versicolor	Iris-versicolor	0.149755725328825	0.681714508186852	0.168529766484323
37	6.7	3.1	4.7	1.5	Iris-versicolor	Iris-versicolor	0.171114811278727	0.609042204950581	0.219842983770691
38	6.9	3.1	5.1	2.3	Iris-virginica	Iris-versicolor	0.219900357496961	0.462897662922802	0.317201979580237
39	6.9	3.1	5.4	2.1	Iris-virginica	Iris-versicolor	0.204584105811045	0.44062725047918	0.354788643709775
40	7.2	3.0	5.8	1.6	Iris-virginica	Iris-versicolor	0.191352800835983	0.409822839002349	0.398824360161668
41	7.7	2.8	6.7	2.0	Iris-virginica	Iris-virginica	0.197515742964366	0.331045470260923	0.471438786774711
42	3.3	4.5	5.6	7.8	Iris-setosa	Iris-setosa	0.396381814771746	0.285670531542205	0.317947653686049
43	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica	0.232107095005353	0.26197205744578	0.505920847548867
44	4.3	4.7	9.6	1.8	Iris-virginica	Iris-virginica	0.232107095005353	0.26197205744578	0.505920847548867

Rows: 1-44 | Columns: 9

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.

model.confusion_matrix()
Out[5]: 
array([[ 7, 10,  0],
       [ 0,  9,  0],
       [ 0,  8, 10]])

Hint

In the context of multi-class classification, you typically work with an overall confusion matrix that summarizes the classification efficiency across all classes. However, you have the flexibility to specify a pos_label and adjust the cutoff threshold. In this case, a binary confusion matrix is computed, where the chosen class is treated as the positive class, allowing you to evaluate its efficiency as if it were a binary classification problem.

Specific confusion matrix:

model.confusion_matrix(pos_label = "Iris-setosa", cutoff = 0.6)
Out[6]: 
array([[27,  0],
       [17,  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(pos_label = "Iris-setosa")

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¶

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

model.contour(pos_label = "Iris-setosa")

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[7]: {'p': 2}

And to manually change some of the parameters:

model.set_params({'p': 3})

Model Register¶

As this model is not native, it does not support model management and versioning. However, it is possible to use the SQL code it generates for deployment.

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[9]: 'CASE WHEN "SepalLengthCm" IS NULL OR "SepalWidthCm" IS NULL OR "PetalLengthCm" IS NULL OR "PetalWidthCm" IS NULL THEN NULL WHEN POWER(POWER("SepalLengthCm" - 5.74090909090909, 2) + POWER("SepalWidthCm" - 3.6469696969697, 2) + POWER("PetalLengthCm" - 7.10606060606061, 2) + POWER("PetalWidthCm" - 1.94242424242424, 2), 1 / 2) <= POWER(POWER("SepalLengthCm" - 4.33582089552239, 2) + POWER("SepalWidthCm" - 3.87910447761194, 2) + POWER("PetalLengthCm" - 3.12985074626866, 2) + POWER("PetalWidthCm" - 3.29701492537313, 2), 1 / 2) AND POWER(POWER("SepalLengthCm" - 5.74090909090909, 2) + POWER("SepalWidthCm" - 3.6469696969697, 2) + POWER("PetalLengthCm" - 7.10606060606061, 2) + POWER("PetalWidthCm" - 1.94242424242424, 2), 1 / 2) <= POWER(POWER("SepalLengthCm" - 5.92439024390244, 2) + POWER("SepalWidthCm" - 2.76829268292683, 2) + POWER("PetalLengthCm" - 4.25609756097561, 2) + POWER("PetalWidthCm" - 1.32682926829268, 2), 1 / 2) THEN \'Iris-virginica\' WHEN POWER(POWER("SepalLengthCm" - 5.92439024390244, 2) + POWER("SepalWidthCm" - 2.76829268292683, 2) + POWER("PetalLengthCm" - 4.25609756097561, 2) + POWER("PetalWidthCm" - 1.32682926829268, 2), 1 / 2) <= POWER(POWER("SepalLengthCm" - 4.33582089552239, 2) + POWER("SepalWidthCm" - 3.87910447761194, 2) + POWER("PetalLengthCm" - 3.12985074626866, 2) + POWER("PetalWidthCm" - 3.29701492537313, 2), 1 / 2) THEN \'Iris-versicolor\' ELSE \'Iris-setosa\' END'

To Python

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

X = [[5, 2, 3, 1]]

model.to_python()(X)
Out[11]: array(['Iris-versicolor'], dtype=object)

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, p: int = 2) → None¶: Must be overridden in the child class

Methods

`__init__`([name, overwrite_model, p])	Must be overridden in the child class
`classification_report`([metrics, cutoff, ...])	Computes a classification report using multiple model evaluation metrics (`auc`, `accuracy`, `f1`...).
`confusion_matrix`([pos_label, cutoff])	Computes the model confusion matrix.
`contour`([pos_label, nbins, chart])	Draws the model's contour plot.
`cutoff_curve`([pos_label, nbins, show, chart])	Draws the model Cutoff curve.
`deploySQL`([X, pos_label, cutoff, allSQL])	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`()	`NearestCentroid` models are not stored in the Vertica DB.
`export_models`(name, path[, kind])	Exports machine learning models.
`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`([pos_label, nbins, show, chart])	Draws the model Lift Chart.
`prc_curve`([pos_label, nbins, show, chart])	Draws the model PRC curve.
`predict`(vdf[, X, name, cutoff, inplace])	Predicts using 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, labels, nbins])	Computes a classification report using multiple model evaluation metrics (`auc`, `accuracy`, `f1`...).
`roc_curve`([pos_label, nbins, show, chart])	Draws the model ROC curve.
`score`([metric, average, pos_label, cutoff, ...])	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

object_type