Xvg file format including non-continuous numbers

[wintermute]

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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.

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.

[pjohansson]

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

[wintermute]

Hi Petter,

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