[gmx-users] Re: gmx-users Digest, Vol 104, Issue 94

[申昊]

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> 
> Message: 3
> Date: Thu, 20 Dec 2012 16:06:33 +0100
> From: Erik Marklund <erikm at xray.bmc.uu.se>
> Subject: Re: [gmx-users] using g_analyze for calculating distance
> 	autocorrelation functions
> To: Discussion list for GROMACS users <gmx-users at gromacs.org>
> Message-ID: <FFBD8DEC-FAA1-4C77-90CA-E96C8BD69EC9 at xray.bmc.uu.se>
> Content-Type: text/plain;	charset=utf-8
> 
> It is common to subtract the average value of the data. Hence the ACF usually contain negative values.

Thank you for your reply. And, how to average the values of the data? averaged over the nearest five or ten points or just skip over them?
As i found in the resulted file, the negative points even reach at -0.6. In this case even the averaged data should also contain negative points which can not be negtived.

> 20 dec 2012 kl. 14.30 skrev 申昊:
> 
> > 
> > Dear GROMACS users,
> > 
> > I have been working on calculating distance autocorrelation functions by using g_analyze.
> > The codes i used was 
> > g_analyze -f dist.xvg -ac autocorr.xvg -temp 300.
> > 'dist.xvg' is about the average distance against simulation time. The two columns are both positive datas.
> > However, the result show a mixture of positive and negative datas. In my opinion, the autocorrelation function should be always positive. 
> > 
> > Can anyone help me with that ?
> > 
> > HaoShen
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