[AstroPy] writing 2D string column to fits binary table

[Benjamin Alan Weaver]

Hello y'all,

Please disregard the previous email.  That applies to ASCII tables not
Binary tables.

Ugh, why do they list ASCII tables first?

Kia ora koutou,
Benjamin Alan Weaver


On Tue, Jan 27, 2015 at 7:32 PM, Benjamin Alan Weaver
<benjamin.weaver at nyu.edu> wrote:
> Hello y'all,
>
>> https://archive.stsci.edu/fits/fits_standard/node70.html#SECTION001233130000000000000
>
> The date at the bottom says 1999.  The FITS 3.0 standard from
> 2008-2010 appears to be more consistent with how cfitsio does it (see
> http://fits.gsfc.nasa.gov/standard30/fits_standard30aa.pdf):
>
> Character fields. The value of a character-formatted (Aw) field is a
> character string of width w containing the characters in columns
> TBCOLn through TBCOLn+w − 1. The character string shall be composed of
> the restricted set of ASCII text characters with decimal values in the
> range 32 through 126 (hexadecimal 20 through 7E).
>
> Note the restriction to decimal values > 0.  This would appear to rule
> out ASCII NULL characters.
>
> Kia ora koutou,
> Benjamin Alan Weaver
>
> On Tue, Jan 27, 2015 at 7:29 PM, Stephen Bailey <stephenbailey at lbl.gov> wrote:
>>
>> On Tue, Jan 27, 2015 at 3:45 PM, Erin Sheldon <erin.sheldon at gmail.com>
>> wrote:
>>>
>>> On 1/27/15, Stephen Bailey <stephenbailey at lbl.gov> wrote:
>>> > On Tue, Jan 27, 2015 at 10:28 AM, Erin Sheldon <erin.sheldon at gmail.com>
>>> > wrote:
>>> >
>>> >> Hi Stephen -
>>> >>
>>> >> This is a difficult problem I think.
>>> >>
>>> >> In FITS, the strings must get padded with spaces when written.  That is
>>> >> my
>>> >> understanding of the format.
>>> >>
>>> >
>>> > From
>>> >
>>> > https://archive.stsci.edu/fits/fits_standard/node70.html#SECTION001233130000000000000
>>> > :
>>> >
>>> > 8.3.3 Data Sequence -> 8.3.3.1 Main Data Table  -> Character
>>> >
>>> > If the value of the TFORMn keyword specifies data type A, field n shall
>>> > contain a character string of  zero or more members, composed of  ASCII
>>> > text. This character string may be terminated before the length
>>> > specified
>>> > by the repeat count  by  an ASCII NULL (hexadecimal code 00). Characters
>>> > after the first ASCII NULL are not defined. A string with the number of
>>> > characters specified by the repeat count is not NULL terminated. Null
>>> > strings are defined by the presence of an ASCII NULL as the first
>>> > character.
>>> >
>>> >
>>> > This indicates that padding with NULLs is the correct thing to do when
>>> > the
>>> > string is shorter than the field.  This is also how the data are in the
>>> > ndarray memory and it is distinguishable from the case of strings that
>>> > end
>>> > with trailing spaces when reading it back in.
>>>
>>> Hi Stephen -
>>>
>>> Interesting, compare this to the cfitsio manual
>>>
>>> http://heasarc.nasa.gov/docs/software/fitsio/c/c_user/node24.html
>>>
>>> So this may be cfitsio specific, and perhaps something we should work
>>> around
>>> in fitsio.
>>
>>
>> Gack.  My interpretation of that is that cfitsio is violating the FITS
>> standard by doing something crazy with padding and stripping spaces.  If you
>> have some way of working around that in fitsio, that would be great.
>>
>> Stephen
>>
>>>
>>>
>>> -e
>>>
>>> --
>>> Erin Scott Sheldon
>>> Brookhaven National Laboratory erin dot sheldon at gmail dot com
>>
>>
>>
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>>
>
>
>
> --
> a.k.a. The Dream Weaver
>
> Outside of a dog, a book is man's best friend. Inside of a dog it's
> too dark to read.
>   --Groucho Marx



-- 
a.k.a. The Dream Weaver

Outside of a dog, a book is man's best friend. Inside of a dog it's
too dark to read.
  --Groucho Marx