When running SpectralData_generation_demo.m script there might be the following error:

Error: File: PhotonAttenuation.m Line: 195 Column: 3
"mu" previously appeared to be used as a function or command, conflicting with its use here as the name of a variable.
A possible cause of this error is that you forgot to initialize the variable, or you have initialized it implicitly using load or eval.

Error in geocore_phantom (line 13)
V = PhotonAttenuation(mat_short, E*1e-3, 'mac'); % mass attenuation coef.

The simple solution is to do as suggested - initialise mu with mi = 0; at the line 95 of PhotonAttenuation.m script.