From 1d8da6d77b0e78b32a3afec183155582cd3e9150 Mon Sep 17 00:00:00 2001 From: "Sergey E. Koposov" Date: Mon, 11 Sep 2023 19:08:35 +0100 Subject: [PATCH] Fix #2114 --- py/desispec/trace_shifts.py | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/py/desispec/trace_shifts.py b/py/desispec/trace_shifts.py index 649603906..47dc50c4c 100644 --- a/py/desispec/trace_shifts.py +++ b/py/desispec/trace_shifts.py @@ -671,12 +671,17 @@ def shift_ycoef_using_external_spectrum(psf, xytraceset, image, fibers, # to assign variance to a spectrum (1.48 is MAD factor, # pi/2 is a factor from Stddev[median(N(0,1))] mad_factor = 1.48 + mad = np.maximum(np.median(np.abs(flux - mflux[None, :]), + axis=0), 1e-100) + # I prevent it from being zero to avoid the warning below + # The exact value does not matter as we're comparing to actual + # median(ivar) mivar = np.minimum( np.median(ivar, axis=0) , - 1./mad_factor**2 / np.median(np.abs(flux - mflux[None, :]), - axis=0)**2) * flux.shape[0] * (2. / np.pi) + 1./mad_factor**2 / mad**2) * flux.shape[0] * (2. / np.pi) # finally use use the MAD of the background subtracted spectra to - # assign further variance limit + # assign further variance limit + # this is sort of "effective" noise in the continuum subtracted spectrum mivar = np.minimum(mivar, 1. / mad_factor**2 / np.median(np.abs(mflux))**2) # do not allow negatives mflux[mflux < 0] = 0