
The process of adjusting model parameters to best match experimental data.Parameter fitting is the process of adjusting the internal parameters of a model so that its predictions match experimental data as closely as possible. This is a fundamental step in virtually every quantitative science, from condensed matter physics to drug design. The challenge is that models often have many parameters, and the data may be noisy or incomplete, so finding the best set of values is a nontrivial optimization problem.
The method of least squares, a foundational technique for parameter fitting, was developed by Carl Friedrich Gauss and Adrien-Marie Legendre in the early 19th century.
The process typically involves defining a 'loss function' that quantifies the difference between the model's predictions and the observed data. Then, an optimization algorithm—such as gradient descent or more sophisticated methods—iteratively adjusts the parameters to minimize this loss. In modern practice, this is often done with neural networks, where the parameters are the weights of the network, and the fitting process is called 'training'.
Parameter fitting is used in radiation therapy to calibrate dose prediction models, in quantum chemistry to train neural networks that predict molecular properties, and in materials science to extract elastic properties from geometric measurements.
In physics-informed neural networks, the model is trained to fit data while also satisfying known physical laws, which dramatically reduces the amount of data needed.













