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Re: Renaming tags in an array of structures [message #72525 is a reply to message #72522]

Fri, 17 September 2010 07:16

Michael Williams
Messages: 17
Registered: December 2008

Junior Member

On Sep 17, 3:30 pm, Paul van Delst <paul.vande...@noaa.gov> wrote:
> Michael Williams wrote:
>> I have an array of structures:
>
>> IDL> x = {a: 1, b:2, c: indgen(5)}
>> IDL> xx = replicate(x, 10)
>
>> In this case, I want to rename the 'b' tag to 'foo' and the 'c' tag to
>> bar.
>
> Can one inquire why you would like/need to do this?

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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