<div>Hi Justin and Mark,</div>
<div>Thanks. Actually I made a mistake and it seems going to the zero (even negative!)</div>
<div>--But I wanted to know how I can write my command to get only one graph (average of all instead of all of them). I read the manual chapter-8 and by average I mean I should get one curve starting at 1 and coming down to zero...I also tried </div>

<div> </div>
<div>g_analyze -f coord.xvg -ac autocorr.xvg  -av average.xvg</div>
<div> </div>
<div>but I do not know what is this average file (it is not clearly what I am looking for).</div>
<div>--Also for the same purpose I tried g_rotacf -d ,</div>
<div>first I extract the coordinates of selected atoms into f.xtc and then tried this command:</div>
<div> </div>
<div>g_rotacf  -f f.xtc  -s f.tpr   -n f.ndx  -o retacf.xvg  -d <br></div>
<div>I got an error message that : &quot; Molecule in topology has atom numbers below and above natoms. you are<br>probably trying to use a trajectory which does not match the first 330 atoms<br>of the run input file. You can make a matching run input file with <strong>tpbconv</strong>.&quot;</div>

<div> </div>
<div>But when I used tpbconb to generate new tpr file using my index file, without giving an error it says &quot;0 steps (0 ps) remaining from first run. You have simulated lon enough. not writing tpr file&quot; and nothing has been generated. </div>

<div> </div>
<div>I read this problem from mailing list and people said that I can use pdb/gro file instead. So I modified last gro file and kept the same atoms as my index file (ref.gro) and used it instead of tpr file:</div>
<div>g_rotacf  -f f.xtc  -s ref.gro   -n f.ndx  -o retacf.xvg  -d </div>
<div>But Can not open ref.gro.tpr</div>
<div>So I do not know how to get rid of this error...Thanks in Advance/Jamie<br><br><br><br></div>
<div class="gmail_quote">On Sat, Aug 22, 2009 at 8:19 PM, Mark Abraham <span dir="ltr">&lt;<a href="mailto:Mark.Abraham@anu.edu.au">Mark.Abraham@anu.edu.au</a>&gt;</span> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Justin A. Lemkul wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><br><br>Jamie Seyed wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Hi Justin, 
<div class="im"><br>Thanks again. I made and used coord.xvg with command<br>g_analyze -f coord.xvg -ac autocorr.xvg      and I got a huge file that I think I need to average over it.<br></div></blockquote></blockquote><br>
Huh? The average has nothing to do with calculating the autocorrelation function. There&#39;s a nice long section in the manual about correlation functions. Read it. 
<div class="im"><br><br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Would you please let me know <br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">how I can get a nice average curve? <br></blockquote></blockquote><br></div>Define &quot;average curve&quot;. 
<div class="im"><br><br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Also I can see that all of them starting at 1, but I do not think the average is going to 0 finally (my system is 216 spce water, 20ps). Is this because the simulation time is not long enough?? Many Thanks in Advance/Jamie<br>
</blockquote></blockquote><br></div>I don&#39;t understand your statement.<br><font color="#888888"><br>Mark</font> 
<div>
<div></div>
<div class="h5"><br><br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Not sure, I&#39;ve never tried such an analysis.  20 ps is pretty short, though. Collecting a few ns of data on such a small system should be trivial. Otherwise, give some indication of what&#39;s actually in the coord.xvg file; someone may have an idea as to what&#39;s going on.  I&#39;m not clear what you&#39;re exactly after, an average of the ACF?<br>
<br>-Justin<br><br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">On Sat, Aug 22, 2009 at 6:49 PM, Justin A. Lemkul &lt;<a href="mailto:jalemkul@vt.edu" target="_blank">jalemkul@vt.edu</a> &lt;mailto:<a href="mailto:jalemkul@vt.edu" target="_blank">jalemkul@vt.edu</a>&gt;&gt; wrote:<br>
<br><br><br>   Jamie Seyed wrote:<br><br>       Hi Justin,<br>       Thanks for the answer. I want to calculate auto-correlation<br>       function of R(x,y,z). I mean &lt;R(0).R(t)&gt; , .../Many Thanks in<br>       Advance/Jamie<br>
<br><br>   Coordinates?  Use g_traj.<br><br>   -Justin<br><br>       On Sat, Aug 22, 2009 at 6:40 PM, Justin A. Lemkul<br>       &lt;<a href="mailto:jalemkul@vt.edu" target="_blank">jalemkul@vt.edu</a> &lt;mailto:<a href="mailto:jalemkul@vt.edu" target="_blank">jalemkul@vt.edu</a>&gt;<br>
       &lt;mailto:<a href="mailto:jalemkul@vt.edu" target="_blank">jalemkul@vt.edu</a> &lt;mailto:<a href="mailto:jalemkul@vt.edu" target="_blank">jalemkul@vt.edu</a>&gt;&gt;&gt; wrote:<br><br><br><br>          Jamie Seyed wrote:<br>
<br>              Hi Mark,<br><br>              Thanks for the answers. I want to use g_analyze but it<br>       needs a<br>              file graph.xvg as an input file. How can I get that for<br>              calculation of auto-correlation function? Many Thanks in<br>
              Advance/Jamie<br><br><br>          The graph.xvg file contains the data for which you want to obtain<br>          the autocorrelation function.  Many of the Gromacs analysis tools<br>          produce .xvg files of whatever quantity they are measuring.  I<br>
          suppose it would then be important to figure out what type of<br>       data<br>          you are trying to obtain the autocorrelation function for;<br>       that will<br>          determine which tool to use :)<br>
<br>          -Justin<br><br>              On Fri, Aug 21, 2009 at 7:57 PM, Mark Abraham<br>              &lt;<a href="mailto:Mark.Abraham@anu.edu.au" target="_blank">Mark.Abraham@anu.edu.au</a> &lt;mailto:<a href="mailto:Mark.Abraham@anu.edu.au" target="_blank">Mark.Abraham@anu.edu.au</a>&gt;<br>
       &lt;mailto:<a href="mailto:Mark.Abraham@anu.edu.au" target="_blank">Mark.Abraham@anu.edu.au</a> &lt;mailto:<a href="mailto:Mark.Abraham@anu.edu.au" target="_blank">Mark.Abraham@anu.edu.au</a>&gt;&gt;<br>              &lt;mailto:<a href="mailto:Mark.Abraham@anu.edu.au" target="_blank">Mark.Abraham@anu.edu.au</a><br>
       &lt;mailto:<a href="mailto:Mark.Abraham@anu.edu.au" target="_blank">Mark.Abraham@anu.edu.au</a>&gt;<br>              &lt;mailto:<a href="mailto:Mark.Abraham@anu.edu.au" target="_blank">Mark.Abraham@anu.edu.au</a><br>
       &lt;mailto:<a href="mailto:Mark.Abraham@anu.edu.au" target="_blank">Mark.Abraham@anu.edu.au</a>&gt;&gt;&gt;&gt; wrote:<br><br>                 Jamie Seyed wrote:<br><br>                     Hi Mark,<br>                     Thanks for the information. Actually in 7.4 I<br>
       found only<br>                     g_rotacf and<br>                     g_angle also g_sgangle that calculate rotation and<br>       angle<br>              correlation<br>                     function and in appendix D I could not find related<br>
              topic... I<br>                     appreciate if<br>                     someone gives me more detail to do the job.<br>                     I want to calculate &lt;R(0).R(t)&gt; that R is<br>       coordinates vector<br>
                     R(x,y,z) for<br>                     pure spce water.<br><br><br>                 If that&#39;s an auto-correlation function, then g_analyze<br>       does<br>              the job.<br>                 Searching for &quot;correlation&quot; in the manual was a good<br>
       way to<br>              start.<br>                 That would also have found a whole section devoted to<br>       the topic,<br>                 which is good reading.<br><br><br>                     Also I have a question related to having a<br>
       coordinate file. I<br>                     did a command<br>                     as<br>                     trajconv  -f  md.trr  -n f.ndx  -o md.xtc<br>                     I am supposing in this case md.xtc contains only x,y,z<br>
                     coordinates. Is that<br>                     true?? Many Thanks in Advance/Jamie<br><br><br>                 Yes, since the compression algorithm used for .xtc<br>       only works on<br>                 positions. However it is a lossy compression, and if<br>
       you want<br>                 full-precision positions-only, look at the options in<br>       trjconv -h.<br><br><br>                 Mark<br>                 _______________________________________________<br>                 gmx-users mailing list    <a href="mailto:gmx-users@gromacs.org" target="_blank">gmx-users@gromacs.org</a><br>
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<br>   Justin A. Lemkul<br>   Ph.D. Candidate<br>   ICTAS Doctoral Scholar<br>   Department of Biochemistry<br>   Virginia Tech<br>   Blacksburg, VA<br>   jalemkul[at]<a href="http://vt.edu/" target="_blank">vt.edu</a> &lt;<a href="http://vt.edu/" target="_blank">http://vt.edu/</a>&gt; | (540) 231-9080<br>
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