From 6878af608df4790973a31bc3f2b5a4c2f71fb341 Mon Sep 17 00:00:00 2001
From: Flippchen <91947480+Flippchen@users.noreply.github.com>
Date: Sun, 11 Feb 2024 17:53:25 +0100
Subject: [PATCH] Feature: Added logic behind class weight calculation

---
 utilities/tools.py | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/utilities/tools.py b/utilities/tools.py
index 3fa8af0..4cc8385 100644
--- a/utilities/tools.py
+++ b/utilities/tools.py
@@ -9,6 +9,7 @@
 import os
 import logging
 import platform
+from sklearn.utils.class_weight import compute_class_weight
 
 
 def load_dataset(path: str, batch_size: int, img_height: int, img_width: int, seed: int) -> tuple[tf.data.Dataset, tf.data.Dataset, list]:
@@ -184,6 +185,47 @@ def show_augmented_batch(train_ds, data_augmentation) -> None:
         plt.show()
 
 
+def compute_class_weights(class_names: list, dataset_train: tf.data.Dataset, dataset_val: tf.data.Dataset) -> dict:
+    """
+    Computes the class weights for the dataset
+
+    :param class_names: List of class names
+    :param dataset_train: Train-Dataset to compute the class weights for
+    :param dataset_val: Validation-Dataset to compute the class weights for
+    :return: Dictionary with class weights
+    """
+    class_counts = {class_name: 0 for class_name in class_names}
+
+    for images, label in dataset_train.unbatch():  # Iterate over each instance
+        class_name = class_names[label.numpy()]  # Directly use label to get class name
+        class_counts[class_name] += 1
+
+    class_count_validation = {class_name: 0 for class_name in class_names}
+
+    for images, label in dataset_val.unbatch():  # Iterate over each instance
+        class_name = class_names[label.numpy()]  # Directly use label to get class name
+        class_count_validation[class_name] += 1
+
+    print("Validation Weights:", {class_name: count for class_name, count in class_count_validation.items()})
+    print("Train Weights:", {class_name: count for class_name, count in class_counts.items()})
+
+    # Convert class counts to a list in the order of class names
+    class_samples = np.array([class_counts[class_name] for class_name in class_names])
+
+    # Calculate class weights
+    # This requires the classes to be sequential numbers starting from 0, which they typically are if indexed by class_names
+    class_weights = compute_class_weight(
+        class_weight='balanced',
+        classes=np.arange(len(class_names)),
+        y=np.concatenate([np.full(count, i) for i, count in enumerate(class_samples)])
+    )
+
+    # Convert class weights to a dictionary where keys are numerical class indices
+    class_weight_dict = {i: weight for i, weight in enumerate(class_weights)}
+
+    return class_weight_dict
+
+
 def plot_model_score(history, name: str, model_type: str) -> None:
     """
     Plots the accuracy and loss of the model