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Re: Arrays of Structures [message #52455 is a reply to message #20472]

Thu, 08 February 2007 10:59

Brian Larsen
Messages: 270
Registered: June 2006

Senior Member

Mick,

>
> (I think) I'm following you to here...
>
>> Meaning that structs.a[23] doesn't make sense because structs.a is an
>> int.
>
> ... but this is where you lose me. Doesn't the the first line that you
> showed say that structs.a is an array of 50 ints?
> Maybe I just can't read the output of HELP properly, but struts.a
> certainly sometimes behaves as an array. Try PRINTing it, for
> instance.
> Or let's compare the output of HELP on a real array of 50 ints:

True, this is a little odd. I like to think of structures as a
container holding things like a. In this case a is an integer and you
have an array of the containers. The other way to do it would be
IDL> structs = {a:intarr(50)}
IDL> help, structs
STRUCTS STRUCT = -> <Anonymous> Array[1]
IDL> help, structs, /str
** Structure <84bd4a4>, 1 tags, length=100, data length=100, refs=1:
A INT Array[50]

Where the thing in the container, a, is an integer array and you only
have one container.

The way that I use structures on a day to day basis is that I read in
a satellite data file that has a bunch of fields in certain coordinate
systems, I store all that in a structure, I then call routines to
change around the coordinate systems and add the parameters to the
structure in that routine so that the container now has more stuff in
it. Then I repeat this for lots of things. So the original structure
is not an array but has arrays and scalars in it, then if I want more
files I read them into the same structure making the structure an
array, that still contains scalars and vectors.

IDL> dat=read_sim('2001101131206.sim')
IDL> help, dat
DAT STRUCT = -> <Anonymous> Array[1]
IDL> help, dat, /str
** Structure <82731ec>, 7 tags, length=301112, data length=301108,
refs=1:
THETA FLOAT Array[12540]
R FLOAT Array[12540]
INTENSITY FLOAT Array[12540]
FIELD4 FLOAT Array[12540]
HEADER STRUCT -> <Anonymous> Array[1]
X FLOAT Array[12540]
Y FLOAT Array[12540]

Of course to make it more confusing still there is a structure header
inside my structure dat

IDL> help, dat.header
<Expression> STRUCT = -> <Anonymous> Array[1]
IDL> help, dat.header, /str
** Structure <84d4ccc>, 21 tags, length=152, data length=148, refs=2:
TIME STRING '2001101131206'
FORMAT STRING 'PT'
NITER INT 6
SDEV FLOAT 0.490877
XSTART FLOAT -3.14159
XEND FLOAT 3.14159
YSTART FLOAT 1.00000
YEND FLOAT 7.00000
XLENGTH INT 209
YLENGTH INT 60
XSTORAGE STRING 'POINT'
YSTORAGE STRING 'POINT'
GSTORAGE STRING 'ROW'
ZEROS STRING 'IGNORE'
ORDER STRING 'NEW'
UNFILLED INT 0
BAD FLOAT -5.00000
GMIN FLOAT 0.00000
GMAX FLOAT 1.00000e+30
XCYCLIC STRING 'YES'
YCYCLIC STRING 'NO'

So I print those elements like this:
IDL> print, dat.header.time
2001101131206

We'll get to the bottom of this.

Brian

------------------------------------------------------------ ---------
Brian A. Larsen
Dept. of Physics
Space Science and Engineering Lab (SSEL)
Montana State University - Bozeman
Bozeman, MT 59717

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[Message index]

		Arrays of Structures By: Ben Tupper on Wed, 21 June 2000 00:00
		Re: Arrays of Structures By: news.qwest.net on Thu, 08 February 2007 12:52
		Re: Arrays of Structures By: JD Smith on Thu, 08 February 2007 12:42
		Re: Arrays of Structures By: Paul Van Delst[1] on Fri, 09 February 2007 08:01
		Re: Arrays of Structures By: Mick Brooks on Fri, 09 February 2007 02:13
		Re: Arrays of Structures By: Michael Galloy on Thu, 08 February 2007 12:21
		Re: Arrays of Structures By: news.qwest.net on Thu, 08 February 2007 11:44
		Re: Arrays of Structures By: Paul Van Delst[1] on Thu, 08 February 2007 11:32
		Re: Arrays of Structures By: Mick Brooks on Thu, 08 February 2007 11:27
		Re: Arrays of Structures By: Brian Larsen on Thu, 08 February 2007 11:11
		Re: Arrays of Structures By: news.qwest.net on Thu, 08 February 2007 11:09
		Re: Arrays of Structures By: Paul Van Delst[1] on Thu, 08 February 2007 11:02
		Re: Arrays of Structures By: Brian Larsen on Thu, 08 February 2007 10:59
		Re: Arrays of Structures By: Mick Brooks on Thu, 08 February 2007 10:04
		Re: Arrays of Structures By: Brian Larsen on Thu, 08 February 2007 09:41
		Re: Arrays of Structures By: JD Smith on Fri, 09 February 2007 12:51

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