def _epd_residual(coeffs, mags, fsv, fdv, fkv, xcc, ycc, bgv, bge, iha, izd):
f = _epd_function(coeffs, fsv, fdv, fkv, xcc, ycc, bgv, bge, iha, izd)<EOL>residual = mags - f<EOL>return residual<EOL>
This is the residual function to minimize using scipy.optimize.leastsq.