[Branch]: differential_rotation

This is the feature branch that contains some diff rot code, I think it needs some love so I am opening this so people don't forget about it!!
Could this be handled with a decorator?

On Tue, Nov 4, 2014 at 4:27 PM, wafels <notifications@github.com> wrote:

> In sunpy/image/coalignment.py:
>
> > @@ -44,6 +46,18 @@ def _default_fmap_function(data):
> >      return np.float64(data)
> >
> >
> > +def _is_pixel_unit(a):
> > +    """Tests the input to see if it is an astropy Quantity with units in
> > +    pixels."""
> > +    return (isinstance(a, u.Quantity) and a.unit == 'pix')
> > +
> > +
> > +def _is_arcsec_unit(a):
> > +    """Tests the input to see if it is an astropy Quantity with units in
> > +    arcseconds."""
> > +    return (isinstance(a, u.Quantity) and a.unit == 'arcsec')
>
> Informative errors are good, but as I said, this will add a lot more if
> blocks in the code: if _is_quantity(input_parameters): ....code that I
> don't think should be in an if block else: ValueError('shoulda used
> quantities') I am not sure that the added complexity in every piece of code
> is worth it.
> … <#1497ceb96d8a0da6_>
> On Tue, Nov 4, 2014 at 5:10 PM, Stuart Mumford <notifications@github.com>
> wrote: In sunpy/image/coalignment.py: > @@ -44,6 +46,18 @@ def
> _default_fmap_function(data): > return np.float64(data) > > > +def
> _is_pixel_unit(a): > + """Tests the input to see if it is an astropy
> Quantity with units in > + pixels.""" > + return (isinstance(a, u.Quantity)
> and a.unit == 'pix') > + > + > +def _is_arcsec_unit(a): > + """Tests the
> input to see if it is an astropy Quantity with units in > + arcseconds."""
> > + return (isinstance(a, u.Quantity) and a.unit == 'arcsec') I think we
> probably need a utility function for it so that it is easier to do
> everywhere, the thing with Quantities is because they are so similar to
> floats, also very specific, and new I think it is very important to give
> the user informative errors. -- Reply to this email directly or view it on
> GitHub <https://github.com/sunpy/sunpy/pull/902/files#r19840204>.
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/sunpy/sunpy/pull/902/files#r19841374>.
>