| Re: Speedy way to get compare array elements. . . [message #32828] |
Thu, 14 November 2002 08:51  |
Pavel A. Romashkin
Messages: 531
Registered: November 2000
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Senior Member |
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Darn, you definitely *do* have your own style! I think it speaks for
itself when people refer to you by your first name and everyone knows
who they talk about.
Also, if I happen to come across a tiny piece of extremely fast code
that I can't figure out how it works, I immediately think - Craig or JD.
And if there's COMMONs all over, or Heap_Gcs, or at least obscure
objects - that's gotta be David's :-)
Cheers,
Pavel
Craig Markwardt wrote:
>
> Some people on the newsgroup thing it is too obscure, but heck, I have
> to have something to distinguish my own style.
>
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| Re: Speedy way to get compare array elements. . . [message #32835 is a reply to message #32828] |
Wed, 13 November 2002 20:28  |
Craig Markwardt
Messages: 1869
Registered: November 1996
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Senior Member |
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"Sean Raffuse" <sean@me.wustl.edu> writes:
> Exalted newsgroup,
>
> What is the fastest way to compare two adjacent values in an array?
>
> Something like:
>
> whoa_huge_jump = where(A[i+1]-A[i] GT 500)
I usually use this little bit of magic,
whoa_huge_jump = where(A[1:*]-A GT 500)
Now, if you are a goody goody, the correct way to do the subtraction
is A[1:*]-A[0:N-2], but that can get annoying, especially if you have
to figure out N first. The cool thing about the trick is that IDL
*automatically* truncates the vector A so that it matches the length
of A[1:*].
Some people on the newsgroup thing it is too obscure, but heck, I have
to have something to distinguish my own style.
Craig
--
------------------------------------------------------------ --------------
Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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| Re: Speedy way to get compare array elements. . . [message #33099 is a reply to message #33031] |
Tue, 03 December 2002 22:54 |
marc schellens[1]
Messages: 183
Registered: January 2000
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Senior Member |
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trouble wrote:
> Craig Markwardt <craigmnet@cow.physics.wisc.edu> wrote in message news:<on4raklqpk.fsf@cow.physics.wisc.edu>...
>
>> ...The cool thing about the trick is that IDL *automatically* truncates
>> the vector A so that it matches the length of A[1:*].
>>
>
>
> Ah, but is there any way to not make it do that? Say you have 2
> vectors of different lengths:
>
> x = findgen(50)
> y = findgen(100)
>
> and you want to form z = x * y, but have z the same length as y
> putting zeros where x has no value. The (sorry) way I am doing it is
>
> z = y * 0
> z[0:49] = x * y
>
> which clearly is too much programmer work since I have to get the
> lengths... Any ideas?
>
> Ciao.
I got the impression my news-server is a little slow,
but anyway (as I see no reply so far):
just say:
z[0]=x*y
IDL the copies as many values as there are to z[0] and the
following elements.
marc
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