sum spectrum both in higher count regions close to peaks and in lower count background regions of the spectrum inspection of a single graphical view on the monitor 10 identifies where to set energy rois for maps that are likely to show spatial variation and thus identify regions in the specimen of different composition furthermore the energy of each peak band delineated by ies can be used to identify elements using an interactive cursor on the display and a look up table of elements and line energies while the embodiments describe the invention applied to a 2d spectrum image it can equally be applied to any set of spectra governed by poisson counting statistics where it is desired to identify parameter values of the spectrum that show significant variation throughout the data set x ray gamma ray optical photons or electrons ions or other fundamental particles may be counted and the spectrum can be any one dimensional array of count values obtained for an increasing sequence of another variable e g wavelength time temperature voltage magnetic field where it is desirable to find for what intervals of this variable there is significant variation in the set of spectra the spectra could be from a 3d array of positions a time sequence of spectra a line profile of spectra on the surface of a specimen a depth profile where spectra are obtained at different depths or a set of spectra obtained at different values of a parameter such as temperature magnetic field voltage or current besides eds.