<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi everyone,<div class=""><br class=""></div><div class="">this is my first post to this email list and I am not sure, if it is the right place to do so. If this is not the case I want to apologize for wasting everyones time, but here we go:</div><div class=""><br class=""></div><div class="">I spent the last days with writing some custom trajectory analysis tools based on the provided file template.cpp. Everything worked well until the time I wanted to access the velocities of my positions in a selection. </div><div class=""><br class=""></div><div class="">Every time I use the function <span style="font-family: Menlo; font-size: 11px;" class="">gmx::SelectionPosition::v()</span> to access the velocity of a position the return value is zero. Of course I added the option <span style="font-family: Menlo; font-size: 11px;" class="">evaluateVelocities() </span>to the selection and checked if there are velocities available in this selection using <font class=""><font face="Menlo" style="font-size: 11px;" class="">Selection::</font><font style="text-decoration: none; background-color: rgb(249, 250, 252);" class=""><font color="#000000" style="font-size: 11px; font-family: Menlo;" class="">hasVelocities</font><font face="Menlo" style="font-size: 11px;" class="">() </font>before calling<font face="Menlo" style="font-size: 11px;" class=""> v(). </font></font></font>I am also positive that the velocities in the provided trajectory are non-zero. Still the function returns zero in every frame of the trajectory and for every position in the selection.</div><div class=""><br class=""></div><div class="">Most probably this is due to a stupid error in my program code, but as there is no working example I know of I am not able to solve this problem on my own. Instead of discussing my program in unnecessary depth, I just ask the following question that simplifies the problem:</div><div class=""><br class=""></div><div class="">What are <i class="">all </i>the necessary changes in the template for the custom trajectory analysis tool to access the velocity of specific positions in the reference and the selection using the function <span style="font-family: Menlo; font-size: 11px;" class="">gmx::SelectionPosition::v()?</span></div><div class=""> </div><div class="">Every help is appreciated. Thanks in advance</div><div class=""><br class=""></div><div class="">Tobias</div></body></html>