| Re: array dimensions [message #24659 is a reply to message #24591] |
Mon, 09 April 2001 09:25   |
John-David T. Smith
Messages: 384
Registered: January 2000
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Senior Member |
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Paul van Delst wrote:
>
> Martin Schultz wrote:
>>
>> "Richard G. French" wrote:
>>>
>>> David Fanning wrote:
>>>> > dimensions = Size(myarray, /Dimensions)
>>>>
>>>> Cheers,
>>>
>>> David is the master of keywords - I've used SIZE all these years without
>>> knowing that there was a /DIMENSIONS keyword. I guess the only way to
>>> know about these things is to read through the documentation over and
>>> over again and take notes on potentially useful keywords and options.
>>>
>>> Which brings me to my question - does anyone out there have a favorite
>>> keyword on a routine that we mere mortals might not know about, but
>>> which
>>> might make our lives much easier? Any suggestions welcome, except for
>>> HISTOGRAM and PLOT!
>>>
>>> Dick French
>>
>> Not a favorite keyword, but a favorite tool: Get a decent system (if
>> you haven't one), install emacs with idlwave, run the routine-info
>> collection, and then you have all the keywords you never knew but
>> always dreamt about literally at your fingertips.
>
> Similar to typing "?" at the IDL prompt and getting similar info - with examples no less!
> Gasp!
Not even *sort of* similar. Yes, it's the same information (Carsten
simply process the pdf manuals to get the documentation). But the
access is amazingly better. Example:
IDL> d=size(myvar,/
Hmm what was that keyword to size? I'll hit [Tab] to see. Up comes:
Possible completions are:
DIMENSIONS FILE_LUN
L64 N_DIMENSIONS
N_ELEMENTS STRUCTURE
TNAME TYPE
Aha, DIMENSIONS, I think that's it. Why don't I right click on it to
find out. Up pops in the help window with help on size() displayed, and
queued up to:
DIMENSIONS
Set this keyword to return the dimensions
of Expression. If Expression is scalar, the
result is a scalar containing a 0. For arrays,
the result is an array containing the array
dimensions. ...
OK, dimensions it is, middle click on it:
IDL> d=size(myvar,/DIMENSIONS
Aren't there some other arguments to size()? I don't recall. I'll just
show the calling syntax. [C-c ?]. Here comes:
Usage: Result = SIZE( Expression)
Keywords: DIMENSIONS FILE_LUN L64 N_DIMENSIONS N_ELEMENTS STRUCTURE
TNAME TYPE
Source: Builtin
Hmm. I guess not. But what is that STUCTURE keyword all about. I don't
remember that one. Why not right click on it (it's blue, which means it
exists in the help).
STRUCTURE
Set this keyword to return all available
information about Expression in a structure.
OK, I'll file that away for a rainy day. As you can see, you soon
become intimately aware of all the keywords in all your favorite
routines, and able to summon them into existence with a few keystrokes.
One positive side effect of keyword completion is that I am no longer
lazy when it comes to partial keywords (OK I'm still lazy, but IDLWAVE
is not). No longer is my code littered with framents like
"a=size(var,/DIME)" and other non-sequiturs.
This is not to mention help with finding the correct routine in the
first place. I haven't thrown away my regular on-line data-files, I
just visit them only about once a month.
To see (and work through) even more examples, have a look at the
tutorial:
http://www.strw.LeidenUniv.nl/~dominik/Tools/idlwave/idlwave .html#SEC3
JD
P.S. There are a couple of new features in the offing for an IDLWAVE
release. If you've ever been tired of the wait for routine info to
load, look for a nice improvement "real soon now". A nice new
drag-to-print feature for instant debugging fun is also in the works.
Stay tuned.
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