SMOTE

This node oversamples the input data (i.e. adds artificial rows) to enrich the training data. The applied technique is called SMOTE (Synthetic Minority Over-sampling Technique) by Chawla et al.

Some supervised learning algorithms (such as decision trees and neural nets) require an equal class distribution to generalize well, i.e. to get good classification performance. In case of unbalanced input data, for instance there are only few objects of the "active" but many of the "inactive" class, this node adjusts the class distribution by adding artificial rows (in the example by adding rows for the "active" class).

The algorithm works roughly as follows: It creates synthetic rows by extrapolating between a real object of a given class (in the above example "active") and one of its nearest neighbors (of the same class). It then picks a point along the line between these two objects and determines the attributes (cell values) of the new object based on this randomly chosen point.

Options

Class Column: Pick the column that contains the class information.
Nearest neighbor: An option that determines how many nearest neighbors shall be considered. The algorithm picks an object from the target class, randomly selects one of its neighbors and draws the new synthetic example along the line between the sample and the neighbor.
Oversample by: Checking this option oversamples each class equally. You need to specify how much synthetic data is introduced, e.g. a value of 2 will introduce two more portions for each class (if there are 50 rows in the input table labeled as "A"; the output will contain 150 rows belonging to "A").
Oversample minority classes: This option adds synthetic examples to all classes that are not the majority class. The output contains the same number of rows for each of the possible classes.
Enable static seed: Check this option if you want to use a seed for the random number generator. This will cause consecutive runs of the node to produce the same output data. If unchecked, each run of the node generates a new seed. Use "Draw new seed" to randomly draw a new seed.

Input Ports

: Table containing labeled data for oversampling.

Output Ports

: Oversampled data (input table with appended rows).

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Installation

To use this node in KNIME, install the extension KNIME Base nodes from the below update site following our NodePit Product and Node Installation Guide:

v5.1

A zipped version of the software site can be downloaded here.

Plugin provider: KNIME AG, Zurich, Switzerland

Plugin version: 5.1.1.v202308221556

On NodePit since: 2023-07-15

Last update: 2023-10-02

KNIME versions: Since v3.6

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