Fitting four-modal sedimentary grain-size distribution with gradient descent method

Gradient descent (GD) method is used to fit the the laser grain-size distribution of the sediments with a sum of four weighted lognormal functions. The numerical results indicate that the GD method is not only easy to operate but also could effectively optimize the parameters of the fitting function with the error decreasing steadily. Meanwhile the overall fitting results are satisfactory. As a new way of data fitting, the GD method could also be used to solve other optimization problems.