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import numpy as np
import matplotlib.pyplot as plt
from sklearn.datasets import load_iris
from sklearn.neighbors import KNeighborsClassifier
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# Load the Iris dataset
iris = load_iris()
X = iris.data[:, :2]  # Use only the first two features
y = iris.target
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# Create a k-NN classifier
knn = KNeighborsClassifier(n_neighbors=3)
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# Train the classifier on the dataset
knn.fit(X, y)
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# Generate a new data point for prediction
new_data_point = np.array([[5.0, 3.5]])  # Example new data point
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# Predict the class of the new data point
predicted_class = knn.predict(new_data_point)
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# Scatter plot of the dataset with two classes and the predicted class of the new data point
plt.figure(figsize=(8, 6))
plt.scatter(X[y == 0, 0], X[y == 0, 1], color='red', label='Setosa')
plt.scatter(X[y == 1, 0], X[y == 1, 1], color='blue', label='Versicolor')
plt.scatter(new_data_point[:, 0], new_data_point[:, 1], color='green', label=f'Predicted: {predicted_class[0]}')
plt.xlabel('Sepal Length (cm)')
plt.ylabel('Sepal Width (cm)')
plt.title('Scatter Plot of Iris Dataset (Setosa vs Versicolor)')
plt.legend()
plt.grid(True)
plt.show()















import numpy as np
import matplotlib.pyplot as plt
from sklearn.datasets import load_iris
from sklearn.neighbors import KNeighborsClassifier
from sklearn.model_selection import train_test_split

# Load the Iris dataset
iris = load_iris()
X = iris.data[:, :2]  # Use only the first two features
y = iris.target

# Split the dataset into training and testing sets
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)

# Define a range of k values to test
k_values = range(1, 21)
accuracies = []

# Iterate over different values of k
for k in k_values:
    # Create a k-NN classifier
    knn = KNeighborsClassifier(n_neighbors=k)
    
    # Train the classifier on the training data
    knn.fit(X_train, y_train)
    
    # Make predictions on the test data
    y_pred = knn.predict(X_test)
    
    # Calculate the accuracy of the model
    accuracy = np.mean(y_pred == y_test)
    accuracies.append(accuracy)

# Plot accuracy versus k
plt.figure(figsize=(8, 6))
plt.plot(k_values, accuracies, marker='o')
plt.xlabel('Number of Neighbors (k)')
plt.ylabel('Accuracy')
plt.title('Accuracy vs Number of Neighbors (k) for Iris Dataset')
plt.xticks(k_values)
plt.grid(True)
plt.show()