Merge pull request #437 from lsst/tickets/SP-1776

SP-1776 : interpret LF as cumulative and use appropriately
lsst · Jan 13, 2025 · 15fcf12 · 15fcf12
2 parents f881cfa + e0c3b84
commit 15fcf12
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/rubin_sim/maf/metrics/crowding_metric.py b/rubin_sim/maf/metrics/crowding_metric.py
@@ -36,6 +36,10 @@ def _comp_crowd_error(mag_vector, lum_func, seeing, single_mag=None):
     mag_uncert : `np.array` (N,)
         Magnitude uncertainties.
     """
+    # Our saved luminosity functions are cumulative,
+    # so we must here convert to differential
+    lum_func = np.diff(lum_func)
+    mag_vector = mag_vector[1:]
     lum_area_arcsec = 3600.0**2
     lum_vector = 10 ** (-0.4 * mag_vector)
     coeff = np.sqrt(np.pi / lum_area_arcsec) * seeing / 2.0