System and methods for identifying nucleotides based on data acquired from a sensor during sequencing of nucleic acids. The method may include obtaining characteristics of light detected from luminescent labels associated with the nucleotides during nucleotide incorporation events. The characteristics may include, for each nucleotide incorporation event, a temporal characteristic the light and an intensity characteristic of the light. The temporal characteristic representing a speed of decay of a probability of photon emission by a luminescent label after excitation. The method may further include grouping points representing the characteristics of the nucleotide incorporation events into groups of points. The individual points may represent at least the temporal characteristic and the intensity characteristic for a corresponding nucleotide incorporation event. The method may further include assigning the groups of points to individual nucleotides.