If you mean, dN/dE as the (energy spectrum of particles), you first get the amount of energy per particle, according to EPOCH simulation. For simplicity, you need to save these acquired energy values in a text file such as ".txt" or ".dat". In Matlab, you have to write the algorithm in such a way that it reads the text file and counts the number of particles which have a certain energy limit. For example, considering the number of zero for particles, add “x” units to the number of particles when the particles’ energy is between E and E+dE. Please note that the numerical value of “x” and "dE" will vary depending on the accuracy of the particle count in your research work.