# Xvg file format including non-continuous numbers

**URL:** <https://gromacs.bioexcel.eu/t/xvg-file-format-including-non-continuous-numbers/4103>\
**Category:** User discussions\
**Tags:** analysis-tools\
**Created:** [May 3, 2022, 2:38pm UTC](https://gromacs.bioexcel.eu/t/xvg-file-format-including-non-continuous-numbers/4103 "2022-05-03T14:38:23Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![wintermute](https://avatars.discourse-cdn.com/v4/letter/w/e19b73/32.png) [@wintermute](https://gromacs.bioexcel.eu/u/wintermute)\
**Post date:** [May 3, 2022, 2:38pm UTC](https://gromacs.bioexcel.eu/t/xvg-file-format-including-non-continuous-numbers/4103/1 "2022-05-03T14:38:23Z")

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GROMACS version:  
GROMACS modification: Yes/No  
Here post your question

Hi there, I was just wondering why in the xvg file (such as rmsd.xvg) the numbers in the first column of the tabular data as shown in the figure below are not always continuous? If I understand it correctly the first column indicates the simulation time/step while the second one is rmsd/rmsf etc.

 ![Screenshot 2022-05-03 at 15.36.47](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/5/5691239a1bdb707bf1d3ae5cee640a3f6be30df1.png)  
0.5100001

As shown in the highlight, it’s 0.5100001 instead of 0.5100000 and I wonder if there is any specific reason for that. Many thanks.

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**Author:** ![pjohansson](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/pjohansson/32/316_2.png) [@pjohansson](https://gromacs.bioexcel.eu/u/pjohansson)\
**Post date:** [May 3, 2022, 2:52pm UTC](https://gromacs.bioexcel.eu/t/xvg-file-format-including-non-continuous-numbers/4103/2 "2022-05-03T14:52:58Z")

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Hi,

the reason is due to imprecision in floating point numbers. In this case the number of decimals written in the .xvg file is larger than the number can accurately represent with 32 bits, so the error becomes apparent (if very minor).

Petter

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**Author:** ![wintermute](https://avatars.discourse-cdn.com/v4/letter/w/e19b73/32.png) [@wintermute](https://gromacs.bioexcel.eu/u/wintermute)\
**Post date:** [May 4, 2022, 5:15pm UTC](https://gromacs.bioexcel.eu/t/xvg-file-format-including-non-continuous-numbers/4103/3 "2022-05-04T17:15:47Z")

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Hi Petter,

Thank you very much for your explanation. It makes sense to me now.