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Re: Data clustering


From: Przemek Klosowski
Subject: Re: Data clustering
Date: Mon, 23 Jun 2014 14:41:51 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0

On 06/23/2014 11:06 AM, CdeMills wrote:

data.data <http://octave.1599824.n4.nabble.com/file/n4664952/data.data>  

Any idea on how to automatically cluster such kind of data ?

findpeaks(abs(diff(Signal)))

using findpeaks from the signal toolbox, except that it's touchy and works on its demo data but throws error on this dataset that actually looks promising when plotted:

error: findpeaks: subscript indices must be either positive integers or logicals
error: called from:
error:   /usr/share/octave/packages/signal-1.2.2/findpeaks.m at line 126, column 5

Does anyone understand why we're getting this error?

BTW, diff(Signal) has one less datapoint than Signal, so it really should be [0; diff(Signal)]. This comes up often, for instance when plotting: plot(x,y,x,diff(y)) doesn't work, so I just write plot(x,y,x,[0;diff(y)]).

I suppose one could argue that mathematically, the more correct plot is

plot(x,y,x(1:end-1)+diff(x)/2,diff(y))

but this is such a common calculation that maybe someone can suggest a more concise way of writing either the shorter X vector or adding one extra point on Y.

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