1. A machine implemented method adapted to a particle analyzer for discriminating particle groups, the method comprising: using the particle analyzer which comprises an electrical power source and is configured for performing a process that comprises: generating, based at least in part on characteristics of particles and a particle count within a sample to be measured, a particle characteristic distribution histogram, wherein a first direction coordinate of the particle characteristic distribution histogram indicates channels for representing the characteristics of the particles, and a second direction coordinate indicates the particle count; setting a valid area selection height in the particle characteristics distribution histogram; generating an equivalent negative histogram based at least in part on the valid area selection height and the particle characteristic distribution histogram, wherein a first height value of a first bar in the equivalent negative histogram for a certain channel equals the valid area selection height minus a second height value of a second bar in the particle characteristic histogram for the channel; and processing the equivalent negative histogram to obtain a dividing line between the particle groups.