# Mismatch between gmx energy and gmx analyze

**URL:** <https://gromacs.bioexcel.eu/t/mismatch-between-gmx-energy-and-gmx-analyze/7189>\
**Category:** User discussions\
**Tags:** analysis-tools\
**Created:** [September 14, 2023, 1:40pm UTC](https://gromacs.bioexcel.eu/t/mismatch-between-gmx-energy-and-gmx-analyze/7189 "2023-09-14T13:40:57Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![MichelePellegrino](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/michelepellegrino/32/628_2.png) [@MichelePellegrino](https://gromacs.bioexcel.eu/u/MichelePellegrino)\
**Post date:** [September 14, 2023, 1:40pm UTC](https://gromacs.bioexcel.eu/t/mismatch-between-gmx-energy-and-gmx-analyze/7189/1 "2023-09-14T13:40:57Z")

</div>

GROMACS version: 2023  
GROMACS modification: Yes

I am computing the surface tension of a biphase system. When I run `gmx energy` I get:

```auto
$ gmx energy -f ener.edr -s system.tpr -o surf-tens.xvg -b 5000
                     :-) GROMACS - gmx energy, 2024-dev (-:

Executable: /usr/local/gromacs/bin/gmx
Data prefix: /usr/local/gromacs
Working dir: /home/michele/python_for_md/PentanolOPLSAA/NVT-surftens
Command line:
  gmx energy -f ener.edr -s system.tpr -o surf-tens.xvg -b 5000

Opened ener.edr as single precision energy file

Select the terms you want from the following list by
selecting either (part of) the name or the number or a combination.
End your selection with an empty line or a zero.
-------------------------------------------------------------------
  1 Bond 2 Angle 3 Ryckaert-Bell. 4 LJ-14         
  5 Coulomb-14 6 LJ-(SR) 7 Disper.-corr. 8 Coulomb-(SR)  
  9 Coul.-recip. 10 Potential 11 Kinetic-En. 12 Total-Energy  
 13 Conserved-En. 14 Temperature 15 Pres.-DC 16 Pressure      
 17 Constr.-rmsd 18 Vir-XX 19 Vir-XY 20 Vir-XZ        
 21 Vir-YX 22 Vir-YY 23 Vir-YZ 24 Vir-ZX        
 25 Vir-ZY 26 Vir-ZZ 27 Pres-XX 28 Pres-XY       
 29 Pres-XZ 30 Pres-YX 31 Pres-YY 32 Pres-YZ       
 33 Pres-ZX 34 Pres-ZY 35 Pres-ZZ 36 #Surf*SurfTen 
 37 T-System 38 Lamb-System   

36

Back Off! I just backed up surf-tens.xvg to ./#surf-tens.xvg.4#
Last energy frame read 15000 time 30000.000         

Statistics over 12500001 steps [5000.0000 through 30000.0000 ps], 1 data sets
All statistics are over 125001 points

Energy Average Err.Est. RMSD Tot-Drift
-------------------------------------------------------------------------------
#Surf*SurfTen 119.55 8 3483.46 -40.5338 (bar nm)

GROMACS reminds you: "If You Don't Like Cool Quotes Check Your GMXRC File" (Your Sysadmin)

```

But if I run `gmx analyze` on the same file I get:

```auto
$ gmx analyze -av -f surf-tens.xvg 
                    :-) GROMACS - gmx analyze, 2024-dev (-:

Executable: /usr/local/gromacs/bin/gmx
Data prefix: /usr/local/gromacs
Working dir: /home/michele/python_for_md/PentanolOPLSAA/NVT-surftens
Command line:
  gmx analyze -av -f surf-tens.xvg

Read 1 sets of 12501 points, dt = 2

                                      std. dev. relative deviation of
                       standard --------- cumulants from those of
set average deviation sqrt(n-1) a Gaussian distribition
                                                      cum. 3 cum. 4
SS1 1.260886e+02 3.450936e+03 3.086611e+01 0.010 -0.012

Back Off! I just backed up average.xvg to ./#average.xvg.4#

GROMACS reminds you: "Torture numbers, and they'll confess to anything." (Greg Easterbrook)

```

I guess the missmatch is due to `gmx analyze` using only roughly 1/10 of the data, but why is it so?