# Gmx trjcat **URL:** \ **Category:** User discussions\ **Tags:** analysis-tools\ **Created:** [March 24, 2024, 1:58pm UTC](https://gromacs.bioexcel.eu/t/gmx-trjcat/8686 "2024-03-24T13:58:41Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Alzahra](https://avatars.discourse-cdn.com/v4/letter/a/71e660/32.png) [@Alzahra](https://gromacs.bioexcel.eu/u/Alzahra)\ **Post date:** [March 24, 2024, 1:58pm UTC](https://gromacs.bioexcel.eu/t/gmx-trjcat/8686/1 "2024-03-24T13:58:42Z")
GROMACS version:2023 GROMACS modification: Yes/No I am using gmx trjcat to combine ten trajectories into one (gmx trjcat -f step6\_1.trr step6\_2.trr step6\_3.trr step6\_4.trr step6\_5.trr step6\_7.trr step6\_8.trr step6\_9.trr step6\_10.trr -o ixed.trr -settime) each trajectory is 1ns =1000ps The prompt i got is shown below. after doing this i got an output file ixed.trr and used analysis tool (rms ) (gmx rms -s step6\_1.tpr -f ixed.trr -o rmsd.xvg) then i tried to plot it but what igot is an empty plot what is the problem? Command line: gmx trjcat -f step6\_1.trr step6\_2.trr step6\_3.trr step6\_4.trr step6\_5.trr step6\_7.trr step6\_8.trr step6\_9.trr step6\_10.trr -o ixed.trr -settime ## trr version: GMX\_trn\_file (single precision) Reading frame 1 time 10.000 File Current start (ps) New start (ps) ``` step6_1.trr 0.000 ps Note that major changes are planned in future for trjcat, to improve usability and utility.0 step6_2.trr 0.000 ps 1001 step6_3.trr 0.000 ps 2001 step6_4.trr 0.000 ps 3001 step6_5.trr 0.000 ps 4001 step6_7.trr 0.000 ps 5001 step6_8.trr 0.000 ps 6001 step6_9.trr 0.000 ps 7001 step6_10.trr 0.000 ps 8001 ``` Summary of files and start times used: ``` File Start time Time step ``` * * * ``` step6_1.trr 0.000 ps 10.000 ps step6_2.trr 1001.000 ps 10.000 ps step6_3.trr 2001.000 ps 10.000 ps step6_4.trr 3001.000 ps 10.000 ps step6_5.trr 4001.000 ps 10.000 ps step6_7.trr 5001.000 ps 10.000 ps step6_8.trr 6001.000 ps 10.000 ps step6_9.trr 7001.000 ps 10.000 ps step6_10.trr 8001.000 ps 10.000 ps ``` Back Off! I just backed up ixed.trr to ./#ixed.trr.1# Reading frame 0 time 0.000 lasttime 0 Continue writing frames from step6\_1.trr t=0 ps, frame=0 Last frame 100 time 1000.000 → frame 90 time 900.000 ps Reading frame 0 time 0.000 lasttime 990 Continue writing frames from step6\_2.trr t=1001 ps, frame=100 Last frame 100 time 1000.000 → frame 190 time 1901.000 ps Reading frame 0 time 0.000 lasttime 1991 Continue writing frames from step6\_3.trr t=2001 ps, frame=200 Last frame 100 time 1000.000 → frame 290 time 2901.000 ps Reading frame 0 time 0.000 lasttime 2991 Continue writing frames from step6\_4.trr t=3001 ps, frame=300 Last frame 100 time 1000.000 → frame 390 time 3901.000 ps Reading frame 0 time 0.000 lasttime 3991 Continue writing frames from step6\_5.trr t=4001 ps, frame=400 Last frame 100 time 1000.000 → frame 490 time 4901.000 ps Reading frame 0 time 0.000 lasttime 4991 Continue writing frames from step6\_7.trr t=5001 ps, frame=500 Last frame 100 time 1000.000 → frame 590 time 5901.000 ps Reading frame 0 time 0.000 lasttime 5991 Continue writing frames from step6\_8.trr t=6001 ps, frame=600 Last frame 100 time 1000.000 → frame 690 time 6901.000 ps Reading frame 0 time 0.000 lasttime 6991 Continue writing frames from step6\_9.trr t=7001 ps, frame=700 Last frame 100 time 1000.000 → frame 790 time 7901.000 ps Reading frame 0 time 0.000 lasttime 7991 Continue writing frames from step6\_10.trr t=8001 ps, frame=800 Last frame 100 time 1000.000 → frame 900 time 9001.000 ps Last frame written was 900, time 9001.000000 ps ---
**Author:** ![MagnusL](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/magnusl/32/2380_2.png) [@MagnusL](https://gromacs.bioexcel.eu/u/MagnusL)\ **Post date:** [March 25, 2024, 10:10am UTC](https://gromacs.bioexcel.eu/t/gmx-trjcat/8686/2 "2024-03-25T10:10:29Z")
Firstly, you should be aware that you are only concatenating nine files not ten (step6\_6.trr is missing). Does the trajectory file open in, e.g., vmd?