[AstroPy] Constructing Angle from a tuple specified as sign string plus numbers for degrees, arcmin, arcsec

[Aldcroft, Thomas]

I'll dispense with my standard rant on how moronic sexigesimal is, and
suggest this:

dec = Angle((np.where(t['DE-'] == '-', -1.0, 1.0) * t['DEd'], t['DEm'],
t['DEs']),
            unit='deg')

This relies on a tricky behavior that -0.0 has a sign of -1.  I'm not 100%
sure if that works on all platforms, but it works on 64-bit mac and linux.

- Tom


On Mon, Aug 10, 2015 at 8:19 PM, John Gizis <gizis at udel.edu> wrote:

> "It seems a bit strange that the table format in this case indicates the
> sign of
> the declination as a completely separate field, rather than as just part
> of the
> numeric string.  But I'm not intimately familiar with the quirks of the CDS
> table format. "
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> I don't think is unusual for CDS tables. I always thought it was because
> Fortran77 didn't know -00 is different than +00.
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> On Mon, Aug 10, 2015 at 11:49 AM, Erik Bray <embray at stsci.edu> wrote:
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>> On 08/10/2015 05:26 PM, Eric L. N. Jensen wrote:
>> > Hi all,
>> >
>> > I’m working with a table from CDS (i.e. from an ApJ paper) that
>> specifies the declination coordinate in four separate columns:  a string
>> for the sign of the declination, and three numerical columns for degrees,
>> arcminutes, and arcseconds.  Is there a straightforward way to combine
>> these into a single astropy.coordinates Angle object?  The standard Angle
>> function (constructor?) only accepts a tuple with three entries.
>> >
>> > I guess what I’m looking for is the inverse method of ‘signed_dms’.
>> >
>> > If it’s of use, the table I’m working with is here:
>> http://iopscience.iop.org/0067-0049/184/1/18/fulltext/apjs300673t4_mrt.txt
>> >
>> > Thanks in advance for your help with this,
>>
>> It seems a bit strange that the table format in this case indicates the
>> sign of
>> the declination as a completely separate field, rather than as just part
>> of the
>> numeric string.  But I'm not intimately familiar with the quirks of the
>> CDS
>> table format.  Is that normal?  I wonder if there's a way to get the CDS
>> reader
>> to format those fields as a single column.  Tom Aldcroft would know
>> better.
>>
>> You can instantiate an Angle array using a generator, so you could
>> probably just
>> slurp in the data using a generator expression, allowing you to transform
>> the
>> values one a time while creating the Angle rather than transforming the
>> table
>> all at once first (please bear with the LISPiness of this example):
>>
>> dec = Angle(((int(row[0] + str(row[1])), row[2], row[3])
>>               for row in table['DE-', 'DEd', 'DEm', 'DEs'))
>>
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>> # (Note: originally I used row[2:] above, but there seems to be an
>> unrelated bug
>> involved in taking slices of rows...I'll report on that.)
>>
>> Erik
>>
>> _______________________________________________
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>>
>
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>
> --
> John E. Gizis
> Professor
> Department of Physics and Astronomy
> University of Delaware
>
> 302-831-2668
>
> _______________________________________________
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> AstroPy at scipy.org
> http://mail.scipy.org/mailman/listinfo/astropy
>
>
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