Euclid factors for multirate filter
[lo,mo] = euclidfactors(hm)
[lo,mo] = euclidfactors(hm) returns integer factors lo and mo such that (lo*L)-(mo*M) = -1. L and M are relatively prime and represent the interpolation and decimation factors of the multirate filter hm.
euclidfactors works with the multirate filters mfilt.firfracdecim and mfilt.firfracinterp. You cannot return lo and mo for decimators or interpolators.
Use an FIR fractional decimator, with L = 5 and M = 7, to show what euclidfactors does.
Indeed, (lo*L)-(mo*M) = (4*5)-(3*7) = -1.