parmnames = ['scale', 'center', 'EISF', 'Wtrans', 'Wrot']

scale = parms[0]
center = parms[1]
EISF = parms[2]
Wtrans = parms[3]
Wrot = parms[4]

ymodel = scale*(pan_LORENTZIAN(x, [EISF, center, Wtrans]) + pan_LORENTZIAN(x, [1.0 - EISF, center, Wtrans + Wrot]))
