Question

Please provide your own example of KNN algorithm

Answer 1

KNN algorithm example:

import numpy as np
import matplotlib.pyplot as plt
import pandas as pd

url = "https://archive.ics.uci.edu/ml/machine-learning-databases/iris/iris.data"

# Assign colum names to the dataset
names = ['sepal-length', 'sepal-width', 'petal-length', 'petal-width', 'Class']

# Read dataset to pandas dataframe
dataset = pd.read_csv(url, names=names)

dataset.head()

X = dataset.iloc[:, :-1].values
y = dataset.iloc[:, 4].values

from sklearn.model_selection import train_test_split
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.20)


from sklearn.preprocessing import StandardScaler
scaler = StandardScaler()
scaler.fit(X_train)

X_train = scaler.transform(X_train)
X_test = scaler.transform(X_test)


from sklearn.neighbors import KNeighborsClassifier
classifier = KNeighborsClassifier(n_neighbors=5)
classifier.fit(X_train, y_train)



y_pred = classifier.predict(X_test)


#evaluation

from sklearn.metrics import classification_report, confusion_matrix
print(confusion_matrix(y_test, y_pred))
print(classification_report(y_test, y_pred))

Output: 
[[11  0  0]
   0 13  0]
   0  1  6]]
                 precision   recall   f1-score   support

    Iris-setosa       1.00     1.00       1.00        11
Iris-versicolor       1.00     1.00       1.00        13
 Iris-virginica       1.00     1.00       1.00         6

    avg / total       1.00     1.00       1.00        30