What Confusion Matrix are made from?

[eojaemyeong]

I have been using Ultralytics platform for running train/inference process on Yolov8 model.
After the training process terminates, with the weights file (.pt) created, along all the png/jpg files, I have examined the term Confusion matrix.

Since training process requires training set and validation set, I was wondering which dataset is used to generate Confusion matrix.

Is it only using validation set?
Also, why is it necessary to have a validation set?
How exactly is validation set used during the training process?

If a data is passed through the network, it will back-prop and update the weights after certain number of data are passed, so what difference does training dataset and validation dataset affect on the network's weight?

Thanks!

[glenn-jocher]

@eojaemyeong hello! The confusion matrix is generated using the validation set. It's a visual tool that helps you understand how well your model is performing across different classes. It compares the model's predictions against the true labels from the validation set, showing where the model might be confusing one class for another.

Having a validation set is crucial because it acts as a checkpoint to monitor the model's performance on unseen data, without affecting the training process. It helps in tuning hyperparameters and provides an unbiased evaluation of the model's ability to generalize.

During training, the model learns by adjusting its weights based on the training set. The validation set, however, is used to evaluate the model's performance at the end of each training epoch. It doesn't contribute to weight updates directly. Instead, it's used to monitor for overfitting, where the model performs well on the training data but poorly on new, unseen data. By comparing performance on both the training and validation sets, you can make informed decisions about when to stop training or adjust your approach.

I hope this clarifies your questions! If you need more detailed explanations, feel free to check out our documentation at https://docs.ultralytics.com. 😊