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Re: Approximate convolution - for loop problem [message #64414 is a reply to message #64402]

Sun, 21 December 2008 12:44

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Sam writes:

> Hi David, unfortunately shift() does not do the business for me, as
> these two examples below show. So I'm still a bit stumped here.
>
> ; Array operation I'm trying to execute.
> a=3D[1.,2.,3.,4.]
> for ii=3D1,3 do a[ii] +=3D 0.5*a[ii-1]
> print,a
> 1.00000 2.50000 4.25000 6.12500
>
> ; Attempt to perform this operation with shift()
> a=3D[1.,2.,3.,4.]
> a +=3D 0.5*shift(a,-1)
> print,a
> 2.00000 3.50000 5.00000 4.50000

Humm. Yes, I see what you mean. I think you might
be out of luck without a loop here, since the *next*
calculation depends on the *previous*. I don't see how
it can be done without a loop.

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: Approximate convolution - for loop problem By: Sam on Mon, 22 December 2008 14:19
		Re: Approximate convolution - for loop problem By: Wout De Nolf on Mon, 22 December 2008 01:31
		Re: Approximate convolution - for loop problem By: David Fanning on Sun, 21 December 2008 12:44
		Re: Approximate convolution - for loop problem By: Sam on Sun, 21 December 2008 12:01
		Re: Approximate convolution - for loop problem By: David Fanning on Sun, 21 December 2008 10:03
		Re: Approximate convolution - for loop problem By: Jeremy Bailin on Tue, 23 December 2008 18:27
		Re: Approximate convolution - for loop problem By: andrews32940 on Tue, 23 December 2008 11:46

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