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Re: mean() function [message #46976 is a reply to message #46938]

Fri, 13 January 2006 00:57

Maarten[1]
Messages: 176
Registered: November 2005

Senior Member

savoie@nsidc.org wrote:

> Would you mind explaining this a bit for me? What's a proper running
> average? And why is it better in general?

It assumes that values are resonably close the the average,
mathematically it is equivalent to taking the total, and then dividing,
but it avoids some precision problems.

In IDL code it requires an explicit loop over the data, which is slow.
An alternative is to do everything in double precision, but that is
just postponing the inevitable.

Code to calculate the mean in an array X:

mean = 0.
for ii = 0, n_elements(X)-1 do $
mean += (X[ii] - mean) / (ii + 1)

Maarten

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[Message index]

		mean() function By: biocpu on Tue, 10 January 2006 14:34
		Re: mean() function By: Foldy Lajos on Mon, 16 January 2006 02:27
		Re: mean() function By: Maarten[1] on Mon, 16 January 2006 00:01
		Re: mean() function By: Foldy Lajos on Sun, 15 January 2006 05:53
		Re: mean() function By: Maarten[1] on Fri, 13 January 2006 00:57
		Re: mean() function By: Kenneth P. Bowman on Thu, 12 January 2006 09:07

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