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Knee or elbow detection for curves

Project description


Find the knee of a curve or the elbow of a curve.

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How it works

kneebow builds upon a very simple idea: if we want to find the elbow of a curve, we can simply rotate the data so that curve looks down and then take the minimum value. If we want to find the knee of the curve, we take the maximum value instead. It's as simple as that.


You can install the package via pip:

pip install kneebow

Alternatively, you can also install the latest version from GitHub:

pip install git+


Let's assume, we try to find the elbow of the following data:

import numpy as np
data = np.array([[1, 1], [2, 2], [3, 3], [4, 4], [5, 5], [6, 6], [7, 7], [8, 8],  # linear until (8,8)
                 [9, 16], [10, 32], [11, 64], [12, 128], [13, 256], [14, 512]])   # exponential afterwards

Let's have a peak how this data looks like:


To find the elbow, we create an instance of the Rotor class and use its fit_rotate method:

from kneebow.rotor import Rotor
rotor = Rotor()

Now we can get the index of the elbow as follows:

elbow_idx = rotor.get_elbow_index()
print(elbow_idx)  # 11

The Rotor class also comes with plot methods to inspect the data visually together with the estimated elbow/knee:




Distributed under the MIT License. See LICENSE for more information.

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Files for kneebow, version 0.1.1
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