Numerical determinations of the first derivatives of a melt curve data set are made. A model function, such as a Gaussian Mixture Model (GMM) function, with parameters determined using a Levenberg-Marquardt (LM) regression process is used to find an approximation to the first derivative curve. The maximum values of the numerically determined first derivative values are used as initial conditions for parameters of the model function. The determined parameters provide one or more fractional melting temperature values, which can be returned, for example, displayed or otherwise used for further processing.