[R] Averaging 'blocks' of data

Robert A LaBudde ral at lcfltd.com
Mon Sep 8 05:49:52 CEST 2008

I'm not sure I exactly understand your problem, but if you are 
looking for a recursive algorithm for calculating the average by 
addition of one record only at a time, consider:

y[k] = y[k-1] + (x[k] - y[k-1])/k,      where y(0) = 0, k = 1, 2, ...

At each stage, y[k] = (x[1]+...+x[k])/k.

At 04:46 PM 9/7/2008, Steve Murray wrote:

>Gabor - thanks for your suggestion... I had checked the previous 
>post, but I found (as a new user of R) this approach to be too 
>complicated and I had problems gaining the correct output values. If 
>there is a simpler way of doing this, then please feel free to let me know.
>Dylan - thanks, your approach is a good start. In answer to your 
>questions, my data are 43200 columns and 16800 rows as a data frame 
>- I will probably have to read the dataset in segments though, as it 
>won't fit into the memory!  I've been able to follow your example - 
>how would I be able to apply this technique for finding the average 
>of each 60 x 60 block?
>Any other suggestions are of course welcome!
>Many thanks again,
>R-help at r-project.org mailing list
>PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: ral at lcfltd.com
Least Cost Formulations, Ltd.            URL: http://lcfltd.com/
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Virginia Beach, VA 23464-3239            Fax: 757-467-2947

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