spherical_offsets_to gives error with array: AttributeError: 'Quantity' object has no 'hypot' member

I have followed the example at:

http://docs.astropy.org/en/stable/coordinates/matchsep.html#matching-catalogs

my example/test is:

import astropy
print('astropy.__version__:', astropy.__version__)

from astropy.table import Table
from astropy import units as u
from astropy.coordinates import SkyCoord
from astropy.coordinates import match_coordinates_sky

from astroquery.irsa import Irsa
from astroquery.sdss import SDSS

c = SkyCoord(ra=ra1*u.degree, dec=dec1*u.degree, distance=distance1*u.kpc)  
catalog = SkyCoord(ra=ra2*u.degree, dec=dec2*u.degree, distance=distance2*u.kpc)  
idx, d2d, d3d = c.match_to_catalog_3d(catalog)  

matches = catalog[idx]  
dra, ddec = c.spherical_offsets_to(matches)

no specfic catalogue is used. In my example I use astroquery as shown below:

region_center = SkyCoord(9.81625*u.deg, 0.88806*u.deg, frame='icrs')
allwise_irsa = Irsa.query_region(coordinates=region_center, radius=4*u.arcmin,
                            catalog='wise_allwise_p3as_psd')
print('Number of ALLWISE sources:', len(allwise_irsa))

sdss = SDSS.query_region(coordinates=region_center, radius=4*u.arcmin,
                         spectro=False,
                         photoobj_fields=['ra','dec','u','g','r','i','z'])

ra = allwise_irsa['ra']
dec = allwise_irsa['dec']
radec_allwise = SkyCoord(ra, dec,unit=(u.degree, u.degree), frame='icrs')

ra = sdss['ra']
dec = sdss['dec']
radec_sdss = SkyCoord(ra, dec,unit=(u.degree, u.degree), frame='icrs')

idx, d2d, d3d = match_coordinates_sky(radec_allwise, radec_sdss)

idx, d2d, d3d = radec_allwise.match_to_catalog_sky(radec_sdss)
print('Number of xmatch sources:', len(idx))

matches = radec_sdss[idx]
print('Test single source')
print(matches[0])
print(radec_allwise[0])
dra, ddec = radec_allwise[0].spherical_offsets_to(matches[0])
print('dra, ddec:', dra.arcsec, ddec.arcsec)

print('Test array')
dra, ddec = radec_allwise.spherical_offsets_to(matches)

I am using astropy 1.2.1

Traceback (most recent call last):
  File "spherical_offsets_to_test.py", line 55, in <module>
    dra, ddec = radec_allwise.spherical_offsets_to(matches)
  File "/home/rgm/anaconda/lib/python2.7/site-packages/astropy/coordinates/sky_coordinate.py", line 747, in spherical_offsets_to
    acoord = tocoord.transform_to(aframe)
  File "/home/rgm/anaconda/lib/python2.7/site-packages/astropy/coordinates/sky_coordinate.py", line 403, in transform_to
    new_coord = trans(self.frame, generic_frame)
  File "/home/rgm/anaconda/lib/python2.7/site-packages/astropy/coordinates/transformations.py", line 915, in __call__
    curr_coord = t(curr_coord, curr_toframe)
  File "/home/rgm/anaconda/lib/python2.7/site-packages/astropy/coordinates/transformations.py", line 833, in __call__
    newrep = newrep.represent_as(fromcoord.data.__class__)
  File "/home/rgm/anaconda/lib/python2.7/site-packages/astropy/coordinates/representation.py", line 90, in represent_as
    return other_class.from_cartesian(self.to_cartesian())
  File "/home/rgm/anaconda/lib/python2.7/site-packages/astropy/coordinates/representation.py", line 421, in from_cartesian
    s = np.hypot(cart.x, cart.y)
  File "/home/rgm/anaconda/lib/python2.7/site-packages/astropy/units/quantity.py", line 753, in __getattr__
    attr))
AttributeError: 'Quantity' object has no 'hypot' member`

This is most bizarre. Is it possible to make a simple example without astroquery? Also, what numpy version are you using?

OK, I have used raw numpy and get the same error: see below; i have added a test using the arrays for separation and position_angle and theu seem to work; so the problem is specific to spherical_offsets_to.

I have poked around in the traceback but it is not obviuos to me what is causing the error: AttributeError: 'Quantity' object has no 'hypot' member

from __future__ import (absolute_import, division, print_function,
                        unicode_literals)
"""
http://docs.astropy.org/en/stable/coordinates/matchsep.html#matching-catalogs

"""

import numpy as np

import astropy
print('astropy.__version__:', astropy.__version__)

from astropy import units as u
from astropy.coordinates import SkyCoord
from astropy.coordinates import match_coordinates_sky

def test1():
    """

    """
    ra_center = 180.0
    dec_center = -60.0

    width = 1.0
    ra_width = width * np.cos(np.deg2rad(dec_center))
    dec_width = width
    npoints = 10
    ra1 = np.random.uniform(ra_center - ra_width / 2.0,
                            ra_center + ra_width / 2.0,
                            npoints)

    dec1 = np.random.uniform(dec_center - dec_width / 2.0,
                             dec_center + dec_width / 2.0,
                             npoints)

    ra2 = np.random.uniform(ra_center - ra_width / 2.0,
                            ra_center + ra_width / 2.0,
                            npoints)

    dec2 = np.random.uniform(dec_center - dec_width / 2.0,
                             dec_center + dec_width / 2.0,
                             npoints)
    print('ra1 range:', np.min(ra1), np.max(ra1))
    print('dec1 range:', np.min(dec1), np.max(dec1))
    print('ra2 range:', np.min(ra2), np.max(ra2))
    print('dec2 range:', np.min(dec2), np.max(dec2))

    c = SkyCoord(ra=ra1 * u.degree, dec=dec1 * u.degree)
    catalog = SkyCoord(ra=ra2 * u.degree, dec=dec2 * u.degree)

    idx, d2d, d3d = c.match_to_catalog_sky(catalog)
    matches = catalog[idx]

    sep = c.separation(matches)
    print('Separation range (arcsecs):', np.min(sep.arcsec), np.max(sep.arcsec))

    pa = c.position_angle(matches)
    print('PA range (degrees):', np.min(pa.degree), np.max(pa.degree))

    dra, ddec = c.spherical_offsets_to(matches)

if __name__ == "__main__":
    """

    """

    test1()

@richardgmcmahon

@richardgmcmahon - I've been slow here, but trying to simplify your example further, I see that spherical_offsets_to fails for any non-scalar SkyCoord:

from astropy.coordinates import SkyCoord
sc = SkyCoord('12h00m00s', '+10d00m00s')
sc.spherical_offsets_to(sc)             
# (<Angle 2.5057879273476366e-14 deg>, <Angle 0.0 deg>)
sc = SkyCoord(['12h00m00s'], ['+10d00m00s'])
sc.spherical_offsets_to(sc)                 
# AttributeError: 'Quantity' object has no 'hypot' member

The problem is that a wrong transformation matrix is created, full of Quantity objects. It definitely is higher up than a problem with Quantity...

Still investigating further...

@eteq

OK, this actually happens to be solved already in current master (perhaps somewhat inadvertently...), due to my removal of the use of numpy matrices (#5104). This will be in astropy 1.3, but I don't know whether we now should consider back-porting it to 1.2 (or even 1.0?). @eteq, @astrofrog?

p.s. At the very least we should include some array-shaped test cases, so that we don't regress on this...

Given how close 1.3 is, I think we can probably call this closed if it's fixed for 1.3? spherical_offsets_to is not in 1.0.x, so no need to port it there...

@mhvk

That is, the actual underlying issue. I created #5163 to implement the regression test @mhvk suggested above.

add regression test for issue from astropy#5163

Merge pull request #5519 from eteq/test-for-5163

@richardgmcmahon

With #5519 in and passing, I think this is OK to close, so I will do so. But @richardgmcmahon, if you're still seeing the error in the lastest master, feel free to re-open this!

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spherical_offsets_to gives error with array: AttributeError: 'Quantity' object has no 'hypot' member #5163

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spherical_offsets_to gives error with array: AttributeError: 'Quantity' object has no 'hypot' member #5163

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mhvk commented on Jul 8, 2016

richardgmcmahon commented on Jul 8, 2016

mhvk commented on Aug 11, 2016

mhvk commented on Aug 11, 2016

mhvk commented on Aug 11, 2016

eteq commented on Nov 29, 2016

eteq commented on Nov 29, 2016

eteq commented on Nov 29, 2016

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