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Re: Chunk Array Decimation [message #32421 is a reply to message #32420]

Wed, 09 October 2002 17:19

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Wed, 09 Oct 2002 17:18:45 -0700, JD Smith wrote:

> On Mon, 07 Oct 2002 08:51:21 -0700, Jaco van Gorkom wrote:
>
>> "JD Smith" <jdsmith@as.arizona.edu> wrote in message
>> news:pan.2002.10.04.22.07.45.664757.24772@as.arizona.edu...
>>
>> JD, we mortals need a tutorial or two in order to even begin to
>> understand that Sparse Array trick you pulled there. My humble
>> contribution to this thread is to propose an additional and hopefully
>> simpler (or, more intuitive) algorithm: let us first sort the data
>> array based on the index array, and then use a cumulative total to do
>> the chunking.
>
> Well, think of an array multiplication of a very large array on a very
> long data vector. Consider only the first row. If almost everything in
> the first column is 0., but a few choice 1.'s, that is the same as
> selecting those elements of the data vector and totaling them. If you
> really had to do all the null operations like:

Sorry, meant to say:

"if almost everything in the first *row* is 0.,..."

JD

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[Message index]

		Chunk Array Decimation By: JD Smith on Tue, 01 October 2002 12:32
		Re: Chunk Array Decimation By: JD Smith on Fri, 04 October 2002 15:07
		Re: Chunk Array Decimation By: Jaco van Gorkom on Mon, 07 October 2002 08:51
		Re: Chunk Array Decimation By: JD Smith on Wed, 09 October 2002 17:18
		Re: Chunk Array Decimation By: JD Smith on Wed, 09 October 2002 17:19
		Re: Chunk Array Decimation By: Jaco van Gorkom on Thu, 10 October 2002 07:26
		Re: Chunk Array Decimation By: JD Smith on Thu, 10 October 2002 11:51
		Re: Chunk Array Decimation By: Keflavich on Tue, 18 November 2008 07:21
		Re: Chunk Array Decimation By: Wout De Nolf on Tue, 18 November 2008 02:52
		Re: Chunk Array Decimation By: Keflavich on Mon, 17 November 2008 13:40

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