[gmx-users] g_energy averages
spoel at xray.bmc.uu.se
Wed Jul 17 20:34:48 CEST 2002
On Wed, 2002-07-17 at 20:15, David L. Bostick wrote:
> .. So, if I want to find the standard error in an average value, I just
> take the fluctuation and divide it by sqrt(nsteps)?
> If I get from the energy file
> Energy Average RMSD Fluct.
> #Surf*SurfTen 147.805 2270.69 2263.84
> and the run was over 250000 steps, the standard error is
No you should divide by the sqrt of the number of *independent* data
points. For energy, there is a correlation on the order of a few
picoseconds (depends on system). For e.g. the dipole moment of the box
it is usually 10 ps (can be related to Debye relaxation). g_analyze may
help you estimating errors, but it is not trivial...
Dr. David van der Spoel, Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576, 75123 Uppsala, Sweden
phone: 46 18 471 4205 fax: 46 18 511 755
spoel at xray.bmc.uu.se spoel at gromacs.org http://zorn.bmc.uu.se/~spoel
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