def calc_parameters(mgnt, p, vp, posp, negp):
"""Calculates certain parameters based on passed pixel groups.
p: pixels defined by the polar crown
vp: finite pixels in the polar crown
posp: positive flux pixels in the polar crown
negp: negative flux pixels in the polar crown
"""
swt = 0
meanf = M.nanmean(mgnt.im_raw_u[vp])
meanfc = M.nanmean(mgnt.im_corr[vp])
sumf = M.nansum(mgnt.im_raw_u[vp])
sumfc = M.nansum(mgnt.im_corr[vp])
unsflux = M.nansum(abs(mgnt.mflux_raw[vp]))
unsfluxc = M.nansum(abs(mgnt.mflux_corr[vp]))
sflux = M.nansum(mgnt.mflux_raw[vp])
sfluxc = M.nansum(mgnt.mflux_corr[vp])
posfluxc = M.nansum(mgnt.mflux_corr[posp])
negfluxc = M.nansum(mgnt.mflux_corr[negp])
visarea = M.nansum(mgnt.area[vp])
max_pxflux = M.nanmax(abs(mgnt.mflux_corr[vp]))
max_pxf = M.nanmax(mgnt.im_raw.data[vp])
max_pxfc = M.nanmax(mgnt.im_corr[vp])
# Corrected field might be zero. Replace entries with NaNs.
if unsfluxc == 0.0:
unsfluxc = M(np.nan, np.nan)
sfluxc = M(np.nan, np.nan)
posfluxc = M(np.nan, np.nan)
negfluxc = M(np.nan, np.nan)
max_pxflux = np.nan
swt = 4
var = {'meanf': meanf, 'meanfc': meanfc, 'sumf': sumf, 'sumfc': sumfc,
'unsflux': unsflux, 'unsfluxc': unsfluxc, 'sflux': sflux,
'sfluxc': sfluxc, 'posfluxc': posfluxc, 'negfluxc': negfluxc,
'nvp_px': np.size(vp), 'p_ratio': np.size(vp)/np.size(p),
'visarea': visarea, 'max_pxflux': max_pxflux, 'max_pxf': max_pxf,
'max_pxfc': max_pxfc, 'swt': swt}
return var
