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Re: Renaming tags in an array of structures [message #72522]

Fri, 17 September 2010 07:50

wlandsman
Messages: 743
Registered: June 2000

Senior Member

Check out the ALIAS keyword in mrdfits.pro

; ALIAS The keyword allows the user to specify the column
names
; to be created when reading FITS data. The value of
; this keyword should be a 2xn string array. The first
; value of each pair of strings should be the desired
; tag name for the IDL column. The second should be
; the FITS TTYPE value.

This is probably more efficient than changing the tag names after the
structure has been read, though I realize that you might not know the
names you need until after the file is read. (And I haven't used
the ALIAS keyword much so I can't vouch for it.) --Wayne

On Sep 17, 10:16 am, Michael Williams <mjwilli...@gmail.com> wrote:
>
> I'm reading in a FITS file (data format used in astronomy) that I did
> not create. The library function I'm using to do this (mrdfits from
> astroidl) returns an array of structures. The names of the tags are
> specified in the fits file itself.
>
> It so happens that in this new file I'm working with, these names do
> not match the choices used for the same data in all my other files.
> For example, let's say I want to plot old_data.speed against
> new_data.speed. But new_data doesn't have a .speed tag. It calls
> it .velocity. If it's just one tag and just one case, then hard coding
> something would work, but as the number of tags grows this becomes
> ugly and error prone. It would be much easier and more general to just
> rename tags. Unfortunately that seems to be non-trivial in IDL.
>
> In my case, the best thing to do is probably to edit the FITS file at
> source and change the header so that the tag names match. That may not
> be possible (or desirable from a data purity point of view) in all
> circumstances, and renaming data structures or changing the metadata
> associated with a strucure should of course be possible in a modern
> language! Hence this question :-)
>
> -- Mike

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[Message index]

		Re: Renaming tags in an array of structures By: wlandsman on Fri, 17 September 2010 07:50
		Re: Renaming tags in an array of structures By: Michael Williams on Fri, 17 September 2010 07:16
		Re: Renaming tags in an array of structures By: Paul Van Delst[1] on Fri, 17 September 2010 06:30
		Re: Renaming tags in an array of structures By: Michael Williams on Thu, 16 September 2010 14:18
		Re: Renaming tags in an array of structures By: Michael Williams on Thu, 16 September 2010 14:13
		Re: Renaming tags in an array of structures By: Michael Williams on Thu, 16 September 2010 13:40
		Re: Renaming tags in an array of structures By: Michael Williams on Thu, 16 September 2010 13:33
		Re: Renaming tags in an array of structures By: penteado on Thu, 16 September 2010 12:05
		Re: Renaming tags in an array of structures By: David Fanning on Thu, 16 September 2010 11:50

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