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150 lines
4.6 KiB
Python
150 lines
4.6 KiB
Python
import pandas as pd
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import math
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import matplotlib.pyplot as plt
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from typing import Dict, List
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class dbscan:
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"""
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DBSCAN Algorithm :
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Density-Based Spatial Clustering Of Applications With Noise
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Refer this website for more details : https://en.wikipedia.org/wiki/DBSCAN
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Functions:
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----------
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__init__() : Constructor that sets minPts, radius and file
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perform_dbscan() : Invoked by constructor and calculates the core and noise points and returns a dictionary.
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print_dbscan() : Prints the core and noise points along with stating if the noise are border points or not.
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plot_dbscan() : Plots the points to show the core and noise point.
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To create a object
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------------------
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import dbscan
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obj = dbscan.dbscan(minPts, radius, file)
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obj.print_dbscan()
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obj.plot_dbscan()
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"""
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def __init__(self, minPts: int, radius: int, file: str) -> None:
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"""
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Constructor
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Attributes:
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-----------
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minPts (int) : Minimum number of points needed to be within the radius to considered as core
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radius (int) : The radius from a given core point where other core points can be considered as core
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file (csv) : CSV file location. Should contain x and y coordinate value for each point.
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Example :
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minPts = 4
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radius = 1.9
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file = 'data_dbscan.csv'
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File Structure of CSV Data:
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---------------------------
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_____
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x | y
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-----
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3 | 7
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4 | 6
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5 | 5
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6 | 4
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7 | 3
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-----
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"""
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self.minPts = minPts
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self.radius = radius
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self.file = file
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self.dict1 = self.perform_dbscan()
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def perform_dbscan(self) -> Dict[int, List[int]]:
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"""
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Parameters:
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-----------
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None
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Return:
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--------
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Dictionary with points and the list of points that lie in its radius
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"""
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data = pd.read_csv(self.file)
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minPts = self.minPts
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e = self.radius
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dict1 = {}
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for i in range(len(data)):
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for j in range(len(data)):
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dist = math.sqrt(
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pow(data["x"][j] - data["x"][i], 2)
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+ pow(data["y"][j] - data["y"][i], 2)
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)
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if dist < e:
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if i + 1 in dict1:
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dict1[i + 1].append(j + 1)
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else:
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dict1[i + 1] = [
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j + 1,
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]
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return dict1
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def print_dbscan(self) -> None:
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"""
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Outputs:
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--------
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Prints each point and if it is a core or a noise (w/ border)
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"""
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for i in self.dict1:
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print(i, " ", self.dict1[i], end=" ---> ")
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if len(self.dict1[i]) >= self.minPts:
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print("Core")
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else:
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for j in self.dict1:
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if (
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i != j
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and len(self.dict1[j]) >= self.minPts
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and i in self.dict1[j]
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):
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print("Noise ---> Border")
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break
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else:
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print("Noise")
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def plot_dbscan(self) -> None:
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"""
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Output:
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-------
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A matplotlib plot that show points as core and noise along with the circle that lie within it.
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"""
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data = pd.read_csv(self.file)
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e = self.radius
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for i in self.dict1:
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if len(self.dict1[i]) >= self.minPts:
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plt.scatter(data["x"][i - 1], data["y"][i - 1], color="red")
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circle = plt.Circle(
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(data["x"][i - 1], data["y"][i - 1]), e, color="blue", fill=False
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)
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plt.gca().add_artist(circle)
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plt.text(
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data["x"][i - 1],
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data["y"][i - 1],
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"P" + str(i),
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ha="center",
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va="bottom",
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)
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else:
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plt.scatter(data["x"][i - 1], data["y"][i - 1], color="green")
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plt.text(
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data["x"][i - 1],
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data["y"][i - 1],
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"P" + str(i),
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ha="center",
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va="bottom",
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)
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plt.xlabel("X")
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plt.ylabel("Y")
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plt.title("DBSCAN Clustering")
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plt.legend(["Core", "Noise"])
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plt.show()
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