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snapprop - evaluates global properties of N-body snapshots.


snapprop [parameter=value]


requires NEMO version 3.0.13 or higher.


snapprop uses a bodiesfunc(5falcON) expression to obtain a bodiesfunc(3falcON) function, which is finally evaluated for N-body snapshots and the return value reported to stdout.


Input data are read from file, which must be in NEMO snapshot format. If file=-, input is expected from stdin. Default: required.
expr must be a bodiesfunc(5falcON) expression. It will be used to generate a bodiesfunc(3falcON) function. Default: required.
pars=parameter list
If the bodiesfunc(5falcON) expression given with prop= requires parameters (up to 10), these must be provided (as comma-separated list) with pars=. No Default.
times=time range(s)
Range(s) of simulation times, for which snapshots shall be processed. Default: all.
If true, body data missing from the snapshot but required for the bodiesfunc(3falcON) function are reset to zero, Otherwise an error is issued and no output is made. Default: f.


To find the minimum softening length, type
   snapprop in=data prop="Min{eps}".

To evaluate the mass-weighted mean specific angular momentum of all bodies which rotate prograde around the z-axis, type
   snapprop in=data prop="Mmean{l@lz>0}".

To evaluate the mass within a radius of 0.1 from the origin, type
   snapprop in=data prop="Sum{m@r<$0}" pars=0.1.

To obtain the rms radial velocity of all bound bodies, type
   snapprop in=data prop="sqrt(Mean{vr*vr@E<0})"
(note that for this example the data must contain the body potentials).

To count the number of bodies within four times minimum softening length, type
   snapprop in=data prop="Num{r<#0*Min{eps}}" pars=4.

See also

bodiesfunc(1falcON) , bodiesfunc(5falcON)


Walter Dehnen

Update History

21-jul-2004 Created    WD
20-aug-2004 improved bodiesfunc    WD
07-nov-2004 parameters added, changed cond#expr to expr@cond    WD
12-jul-2006 Updated    WD

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