# About the replicas
**URL:** https://gromacs.bioexcel.eu/t/about-the-replicas/2671
**Category:** User discussions
**Created:** [August 12, 2021, 7:20am UTC](https://gromacs.bioexcel.eu/t/about-the-replicas/2671 "2021-08-12T07:20:41Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@ashkhan](https://gromacs.bioexcel.eu/u/ashkhan)
#### Post date: [August 12, 2021, 7:20am UTC](https://gromacs.bioexcel.eu/t/about-the-replicas/2671/1 "2021-08-12T07:20:41Z")
GROMACS version: 5.1.4
GROMACS modification: Yes/N
Dear all,
We have generated the 10 replicas of 100ns each and for some analysis we have taken the results by averaging of 10 replicas over all time frames, but for more analysis it is not possible to show the average results of all replicas unless we make the average of .xtc file of 10 replicas so that we can use one trajectory file for all other analysis like FEL plot, clustering, etc. Anybody can suggest me, how to make average of .xtc file of 10 replicas for 100 ns?
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### Author:  [@alevilla](https://gromacs.bioexcel.eu/u/alevilla)
#### Post date: [August 17, 2021, 8:33am UTC](https://gromacs.bioexcel.eu/t/about-the-replicas/2671/2 "2021-08-17T08:33:33Z")
Hi,
to concatenate xtc/trr files of the same system you can use gmx trjcat [gmx trjcat — GROMACS 2021.2 documentation](https://manual.gromacs.org/current/onlinehelp/gmx-trjcat.html). Using `-cat` , you can simply paste several files together without removal of frames with identical time stamps.
Kind regards
Alessandra
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### Author:  [@ashkhan](https://gromacs.bioexcel.eu/u/ashkhan)
#### Post date: [August 17, 2021, 1:41pm UTC](https://gromacs.bioexcel.eu/t/about-the-replicas/2671/3 "2021-08-17T13:41:18Z")
Thank you for your response but my problem is that I have created replicas for one system and for analysis I want to use average of these replicas to generate one .xtc file for further use.
How to make averge of replicas .xtc?
I have generated replicas as generated in the given below doi of paper.
> **[Avoiding False Positive Conclusions in Molecular Simulation: The Importance...](https://pubs.acs.org/doi/10.1021/acs.jctc.8b00391)**
>
> Molecular simulations are a computational technique used to investigate the dynamics of proteins and other molecules. The free energy landscape of these simulations is often rugged, and minor differences in the initial velocities, floating-point...