[AstroPy] question about RotateNative2Celestial

[Martin Beroiz]

Hello,

I’m toying a little with WCS and the functions on astropy.modeling.rotations.
I’m not sure if I found a bug or if I don’t understand yet the API for RotateNative2Celestial
Here’s the small example that I came up with and the traceback I get

from astropy.modeling import rotations as r
lon = 100.00
lat = -63.00
alpha_c = 100.00
delta_c = -63.00
lon_pole = 180.0

n2c = r.RotateNative2Celestial(lon, lat, lon_pole)
n2c.evaluate(0., 90., lon, lat, lon_pole)

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-4-0a1e86053054> in <module>
----> 1 n2c.evaluate(0., 90., lon, lat, lon_pole)

~/anaconda3/lib/python3.7/site-packages/astropy/modeling/rotations.py in evaluate(self, phi_N, theta_N, lon, lat, lon_pole)
   252         theta = - (np.pi / 2 - lat)
   253         psi = -(np.pi / 2 + lon)
--> 254         alpha_C, delta_C = super()._evaluate(phi_N, theta_N, phi, theta, psi)
   255         return alpha_C, delta_C
   256

~/anaconda3/lib/python3.7/site-packages/astropy/modeling/rotations.py in _evaluate(self, phi, theta, lon, lat, lon_pole)
   183     def _evaluate(self, phi, theta, lon, lat, lon_pole):
   184         alpha, delta = super().evaluate(phi, theta, lon, lat, lon_pole,
--> 185                                         self.axes_order)
   186         mask = alpha < 0
   187         if isinstance(mask, np.ndarray):

~/anaconda3/lib/python3.7/site-packages/astropy/modeling/rotations.py in evaluate(self, alpha, delta, phi, theta, psi, axes_order)
    89             shape = alpha.shape
    90         inp = self.spherical2cartesian(alpha, delta)
---> 91         matrix = self._create_matrix(phi, theta, psi, axes_order)
    92         result = np.dot(matrix, inp)
    93         a, b = self.cartesian2spherical(*result)

~/anaconda3/lib/python3.7/site-packages/astropy/modeling/rotations.py in _create_matrix(self, phi, theta, psi, axes_order)
    47             if isinstance(angle, u.Quantity):
    48                 angle = angle.value
---> 49             angle = angle.item()
    50             matrices.append(rotation_matrix(angle, axis, unit=u.rad))
    51         result = matrix_product(*matrices[::-1])

AttributeError: 'float' object has no attribute 'item'


I don't understand why it is expecting `angle` to have the `item` attribute.

Does anyone know what I'm doing wrong? Any help would be much appreciated.

Thanks!
M.




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