Add TensorFlow/Keras Neural Networks for Classification

machine_learning/neural_networks/cnn_mnist.py

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+"""
+Convolutional Neural Network (CNN) for MNIST Classification
+
+Goal: This script builds a deep CNN to classify the MNIST dataset using
+    TensorFlow and Keras. It leverages convolutional layers for feature
+    extraction and pooling layers for down-sampling, followed by fully
+    connected layers for classification.
+
+Objectives:
+- Load and preprocess MNIST data (reshape for CNN input).
+- Build a CNN with multiple convolutional, pooling, and batch normalization layers.
+- Train the CNN, evaluate its accuracy, and display model performance.
+
+"""
+
+# import tensorflow as tf
+from tensorflow.keras import layers, models
+from tensorflow.keras.datasets import mnist
+from tensorflow.keras.utils import to_categorical
+
+# Load and preprocess the MNIST data
+(x_train, y_train), (x_test, y_test) = mnist.load_data()
+
+# Normalize the pixel values (0 to 1)
+x_train = x_train.reshape(-1, 28, 28, 1).astype("float32") / 255
+x_test = x_test.reshape(-1, 28, 28, 1).astype("float32") / 255
+
+# Convert labels to one-hot encoding
+y_train = to_categorical(y_train, 10)
+y_test = to_categorical(y_test, 10)
+
+# Building the CNN model
+model = models.Sequential()
+
+# 1st Convolutional Layer
+model.add(layers.Conv2D(32, (3, 3), activation="relu", input_shape=(28, 28, 1)))
+model.add(layers.MaxPooling2D((2, 2)))
+model.add(layers.BatchNormalization())
+
+# 2nd Convolutional Layer
+model.add(layers.Conv2D(64, (3, 3), activation="relu"))
+model.add(layers.MaxPooling2D((2, 2)))
+model.add(layers.BatchNormalization())
+
+# 3rd Convolutional Layer
+model.add(layers.Conv2D(128, (3, 3), activation="relu"))
+model.add(layers.BatchNormalization())
+
+# Flattening the data before fully connected layers
+model.add(layers.Flatten())
+
+# Fully Connected (Dense) Layer with Dropout for regularization
+model.add(layers.Dense(128, activation="relu"))
+model.add(layers.Dropout(0.5))
+
+# Output Layer for classification
+model.add(layers.Dense(10, activation="softmax"))
+
+# Compile the model
+model.compile(optimizer="adam", loss="categorical_crossentropy", metrics=["accuracy"])
+
+# Display the model summary
+model.summary()
+
+# Train the model
+history = model.fit(
+    x_train, y_train, epochs=5, batch_size=32, validation_data=(x_test, y_test)
+)
+
+# Evaluate the model on test data
+test_loss, test_acc = model.evaluate(x_test, y_test, verbose=2)
+print(f"\nTest accuracy: {test_acc}")

machine_learning/neural_networks/fully_connected_mnist.py

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+"""
+Fully Connected Neural Network for MNIST Classification
+
+Goal: This script implements a fully connected feed-forward neural network
+    using TensorFlow and Keras to classify the MNIST dataset
+    (28x28 grayscale images of handwritten digits from 0 to 9).
+    The network has two hidden layers with ReLU activations and dropout
+    for regularization.
+
+Objectives:
+- Normalize and preprocess MNIST data.
+- Build a basic neural network with dense layers.
+- Train the model, evaluate its accuracy and loss at each epoch,
+  and predict sample outputs.
+
+"""
+
+# Standard library imports
+# (None in this case)
+
+# Third-party imports
+import numpy as np
+import tensorflow as tf
+from tensorflow.keras import layers, models
+
+# Load the MNIST dataset from Keras
+mnist = tf.keras.datasets.mnist
+(x_train, y_train), (x_test, y_test) = mnist.load_data()
+
+# Normalize the images from 0-255 to 0-1 by dividing by 255
+x_train, x_test = x_train / 255.0, x_test / 255.0
+
+# Print TensorFlow and Keras information
+print(f"TensorFlow Version: {tf.__version__}")
+print(f"Keras Layers Module: {layers.__name__}")
+print(f"Keras Models Module: {models.__name__}")
+
+# Build a simple Sequential model
+model = models.Sequential()
+
+# Flatten the 28x28 images into vectors of length 784
+model.add(layers.Flatten(input_shape=(28, 28)))
+
+# First hidden layer with 128 neurons and ReLU activation
+model.add(layers.Dense(128, activation="relu"))
+
+# Dropout layer to prevent overfitting (randomly drops 20% of neurons)
+model.add(layers.Dropout(0.2))
+
+# Second hidden layer with 64 neurons and ReLU activation
+model.add(layers.Dense(64, activation="relu"))
+
+# Output layer with 10 neurons (one for each digit class 0-9),
+# softmax for probabilities
+model.add(layers.Dense(10, activation="softmax"))
+
+# Compile the model
+model.compile(
+    optimizer="adam", loss="sparse_categorical_crossentropy", metrics=["accuracy"]
+)
+
+# Train the model on the MNIST training data
+model.fit(x_train, y_train, epochs=5, batch_size=32)
+
+# Evaluate the model on the test set
+test_loss, test_acc = model.evaluate(x_test, y_test, verbose=2)
+print(f"\nTest accuracy: {test_acc}")
+
+# Make a prediction on a random test image
+rng = np.random.default_rng()
+random_index = rng.integers(0, len(x_test))
+random_image = np.expand_dims(x_test[random_index], axis=0)
+prediction = model.predict(random_image)
+predicted_digit = np.argmax(prediction)
+
+# Print the predicted result and actual label
+print(f"Predicted digit: {predicted_digit}, Actual digit: {y_test[random_index]}")