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Fix unit conversion of limits from Fnu to Flam #2889

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merged 4 commits into from
May 31, 2024
Merged

Fix unit conversion of limits from Fnu to Flam #2889

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836bce6
Fix unit conversion from flux to surface brightness
astrofrog May 22, 2024
fc39756
Fix case in to_unit where limits are converted from Fnu to Flam
astrofrog May 22, 2024
77fe6db
change variable name to match PR, speclim->specvalues, value->values
gibsongreen May 31, 2024
c26c5e1
readd accidentally deleted comment
gibsongreen May 31, 2024
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20 changes: 14 additions & 6 deletions jdaviz/app.py
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Original file line number Diff line number Diff line change
Expand Up @@ -112,6 +112,15 @@ def to_unit(self, data, cid, values, original_units, target_units):
eqv = []
else:
eqv = []

# If there are only two values, this is likely the limits being converted, so then
# in case we need to use the spectral density equivalency, we need to provide only
# to spectral axis values. If there is only one value
if not np.isscalar(values) and len(values) == 2:
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spectral_values = spec.spectral_axis[0]
else:
spectral_values = spec.spectral_axis

# Ensure a spectrum passed through Spectral Extraction plugin
if '_pixel_scale_factor' in spec.meta and len(values) != 2:

Expand All @@ -120,26 +129,25 @@ def to_unit(self, data, cid, values, original_units, target_units):
# target_units dictate the conversion to take place.

if (u.sr in u.Unit(original_units).bases) and \
(u.sr not in u.Unit(target_units).bases):
(u.sr not in u.Unit(target_units).bases):
# Surface Brightness -> Flux
eqv = [(u.MJy / u.sr,
u.MJy,
lambda x: (x * np.array(spec.meta['_pixel_scale_factor'])),
lambda x: x)]
elif (u.sr not in u.Unit(original_units).bases) and \
(u.sr in u.Unit(target_units).bases):
(u.sr in u.Unit(target_units).bases):
# Flux -> Surface Brightness
eqv = [(u.MJy,
u.MJy / u.sr,
lambda x: (x / np.array(spec.meta['_pixel_scale_factor'])),
lambda x: x)]
else:
eqv = u.spectral_density(spec.spectral_axis)
eqv = u.spectral_density(spectral_values)

elif len(values) == 2:
# Need this for setting the y-limits
spec_limits = [spec.spectral_axis[0].value, spec.spectral_axis[-1].value]
eqv = u.spectral_density(spec_limits * spec.spectral_axis.unit)
eqv = u.spectral_density(spectral_values)

if '_pixel_scale_factor' in spec.meta:
# get min and max scale factors, to use with min and max of spec for
Expand All @@ -162,7 +170,7 @@ def to_unit(self, data, cid, values, original_units, target_units):
lambda x: x)]

else:
eqv = u.spectral_density(spec.spectral_axis)
eqv = u.spectral_density(spectral_values)

else: # spectral axis
eqv = u.spectral() + u.pixel_scale(1*u.pix)
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29 changes: 29 additions & 0 deletions jdaviz/tests/test_app.py
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Original file line number Diff line number Diff line change
Expand Up @@ -233,3 +233,32 @@ def test_to_unit(cubeviz_helper):
# will be a uniform array since not wavelength dependent
# so test first value in array
assert np.allclose(value[0], 4.800000041882413e-08)

# Change from Fnu to Flam (with values shape matching spectral axis)

values = np.ones(3001)
original_units = u.MJy
target_units = u.erg / u.cm**2 / u.s / u.AA

new_values = uc.to_unit(cubeviz_helper, data, cid, values, original_units, target_units)

assert np.allclose(new_values,
(values * original_units)
.to_value(target_units,
equivalencies=u.spectral_density(cube.spectral_axis)))

# Change from Fnu to Flam (with a shape (2,) array of values indicating we
# are probably converting the limits)

values = [1, 2]
original_units = u.MJy
target_units = u.erg / u.cm**2 / u.s / u.AA

new_values = uc.to_unit(cubeviz_helper, data, cid, values, original_units, target_units)

# In this case we do a regular spectral density conversion, but using the
# first value in the spectral axis for the equivalency
assert np.allclose(new_values,
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([1, 2] * original_units)
.to_value(target_units,
equivalencies=u.spectral_density(cube.spectral_axis[0])))
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