Can't add row to table with, e.g., SkyCoord column #5745

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1. pllim

   added

   table

   time

   on Jan 27, 2017
2. kakirastern commented on Feb 25, 2019

   

   kakirastern

   on Feb 25, 2019

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   Hi, can I work on this Issue?
3. kakirastern commented on Feb 25, 2019

   

   kakirastern

   on Feb 25, 2019

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   I have checked that the same issue persists for astropy v3.2.dev23909. Maybe some documentation to clarify is necessary? Or, can an insert attribute be added to the SkyCoord object as a convenience?

   So in my effort to reproduce the error, if I do the following:

   from astropy.table import Table
   from astropy.time import Time
   from astropy.coordinates import SkyCoord
   tm = Time(['2000:002', '2002:345'])
   sc = SkyCoord([10, 20], [-45, +40], unit='deg')
   t = Table([tm, sc], names=['time', 'skycoord'])
   print(t)
   

   I do indeed get the table:

            time          skycoord 
                          deg,deg  
   --------------------- ----------
   2000:002:00:00:00.000 10.0,-45.0
   2002:345:00:00:00.000  20.0,40.0
   

   And when I tried to use add the row as suggested by @dmopalmer as:

   # Add another row
   t.add_row((Time('2017:001'),sc[0]))
   

   The following errors ensue:

   ---------------------------------------------------------------------------
   AttributeError                            Traceback (most recent call last)
   ~/astropy/astropy/table/table.py in insert_row(self, index, vals, mask)
      2339 
   -> 2340                 newcol = col.insert(index, val, axis=0)
      2341                 if not isinstance(newcol, BaseColumn):
   
   ~/astropy/astropy/coordinates/sky_coordinate.py in __getattr__(self, attr)
       599         raise AttributeError("'{0}' object has no attribute '{1}'"
   --> 600                              .format(self.__class__.__name__, attr))
       601 
   
   AttributeError: 'SkyCoord' object has no attribute 'insert'
   
   During handling of the above exception, another exception occurred:
   
   ValueError                                Traceback (most recent call last)
   <ipython-input-5-a56775b2e898> in <module>
         1 # Add another row
   ----> 2 t.add_row((Time('2017:001'),sc[0]))
   
   ~/astropy/astropy/table/table.py in add_row(self, vals, mask)
      2228              3   6   9
      2229         """
   -> 2230         self.insert_row(len(self), vals, mask)
      2231 
      2232     def insert_row(self, index, vals=None, mask=None):
   
   ~/astropy/astropy/table/table.py in insert_row(self, index, vals, mask)
      2362         except Exception as err:
      2363             raise ValueError("Unable to insert row because of exception in column '{0}':\n{1}"
   -> 2364                              .format(name, err))
      2365         else:
      2366             self._replace_cols(columns)
   
   ValueError: Unable to insert row because of exception in column 'skycoord':
   'SkyCoord' object has no attribute 'insert'
   
4. bsipocz

   changed the title [-]Can't add row to table with, e.g., Time column[/-] [+]Can't add row to table with, e.g., SkyCoord column[/+] on Feb 25, 2019
5. bsipocz

   added

   coordinates

   on Feb 25, 2019
6. bsipocz commented on Feb 25, 2019

   

   bsipocz

   on Feb 25, 2019

   Last edited by bsipocz

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   Thanks @kakirastern for the follow-up. It indeed seems that for Time objects this issue has been solved, but not yet for SkyCoord. I've updated the labels and title accordingly.
7. kakirastern commented on Feb 26, 2019

   

   kakirastern

   on Feb 26, 2019

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   Sure @bsipocz! I will open a PR and try and find a solution soon.
8. kakirastern commented on Mar 9, 2019

   

   kakirastern

   on Mar 9, 2019

   Last edited by kakirastern

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   I found this in the latest docs today: http://docs.astropy.org/en/latest/table/mixin_columns.html#details-and-caveats, which says something like "Adding or inserting a row works as expected only for mixin classes that are mutable (data can changed internally) and that have an insert() method. Quantity and Time support insert() but for example SkyCoord does not. If one tried to insert a row into a table with a SkyCoord column then an exception... would occur." So maybe it would be better to suggest a workaround in the documentation instead of attempting to change the code?
9. kakirastern commented on Mar 9, 2019

   

   kakirastern

   on Mar 9, 2019

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   Or, should I look into adding an insert() method for SkyCoord? Like using something similar to the following for Quantity?:

   def insert(self, obj, values, axis=None):
           """
           Insert values along the given axis before the given indices and return
           a new `~astropy.units.Quantity` object.
   
           This is a thin wrapper around the `numpy.insert` function.
   
           Parameters
           ----------
           obj : int, slice or sequence of ints
               Object that defines the index or indices before which ``values`` is
               inserted.
           values : array-like
               Values to insert.  If the type of ``values`` is different
               from that of quantity, ``values`` is converted to the matching type.
               ``values`` should be shaped so that it can be broadcast appropriately
               The unit of ``values`` must be consistent with this quantity.
           axis : int, optional
               Axis along which to insert ``values``.  If ``axis`` is None then
               the quantity array is flattened before insertion.
   
           Returns
           -------
           out : `~astropy.units.Quantity`
               A copy of quantity with ``values`` inserted.  Note that the
               insertion does not occur in-place: a new quantity array is returned.
   
           Examples
           --------
           >>> import astropy.units as u
           >>> q = [1, 2] * u.m
           >>> q.insert(0, 50 * u.cm)
           <Quantity [ 0.5,  1.,  2.] m>
   
           >>> q = [[1, 2], [3, 4]] * u.m
           >>> q.insert(1, [10, 20] * u.m, axis=0)
           <Quantity [[  1.,  2.],
                      [ 10., 20.],
                      [  3.,  4.]] m>
   
           >>> q.insert(1, 10 * u.m, axis=1)
           <Quantity [[  1., 10.,  2.],
                      [  3., 10.,  4.]] m>
   
           """
           out_array = np.insert(self.value, obj, self._to_own_unit(values), axis)
           return self._new_view(out_array)
   

   Would that work? (I reckon it is more complex than that, but would like to confirm... )
10. bsipocz commented on Mar 9, 2019

    

    bsipocz

    on Mar 9, 2019

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    Or, should I look into adding an insert() method for SkyCoord?

    I would naively say yes, but let's ping the coordinates maintainers @eteq @adrn to comment on it.

    👍React with 👍1Reacted by Kris Stern
11. kakirastern commented on Mar 10, 2019

    

    kakirastern

    on Mar 10, 2019

    Last edited by kakirastern

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    I have a feeling that the code involved to introduce an insert property to SkyCoord would be a lot more complicated than for either Time or Quantity...
12. mhvk

    removed

    time

    on Oct 1, 2019
13. mhvk

    closed this as completedin #9857on Apr 25, 2020