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snapscale - re-scale an N-body system
snapscale in=in_file out=out_file
[parameter=value] ...
snapscale copies an N-body system from in
to out, multiplying various components of the snapshot by their respective
scale factors. All scalings are done independantly, the scalefactors have
to be supplied explicitly. For example, if positions are scaled, velocities
are not (unless specified of course), and are treated as independant. The
default for all scale factors is 1.
For that matter snapscale is not an
intelligent program. One could set it up with default not supplied (empty
keywords), and let the program figure out how to rescale all available
items in the snapshot if e.g. only masses are scaled, and virial units are
to be effective, the radii and/or velocities will also be appropriately
scaled. These features are implemented in snapvirial.
The following
parameters are recognized:
- in=in_file
- input file, in snapshot(5NEMO)
format.
Default: none.
- out=out_file
- output file, also snapshot format. Default:
none.
- mscale=m_scale_factor
- Scale factor for particle masses. Default: 1.0.
- rscale=pos_scale_factor(s)
- Scale factor for position space. If three numbers
are given, the three positions are scaled independantly. One number means
all NDIM (three or two) coordinates are transformed the same. Default: 1.0.
- vscale=vel_scale_factor(s)
- Scale factor for velocity space. If three numbers
are given, the three velocities are scaled independantly. One number means
all NDIM (three or two) coordinates are transformed the same. Default: 1.0.
- pscale=phi_scale_factor
- Scale factor for particle potentials. Default:
1.0.
- ascale=acc_scale_factor(s)
- Scale factor for accelerations. If three
numbers are given, the three accelerations are scaled independantly. One
number means all NDIM (three or two) coordinates are transformed the same.
Default: 1.0.
- xscale=aux_scale_factor
- Scale factor for the auxilliary information
item, if present. Default: 1.0.
- kscale=key_scale_factor
- Scale factor for
the key item. Note that this item must be an integer. Default: 1.
- times=time-ranges
- Only snapshots with time values within times-ranges, which is of the form
ts[:te],..., will be copied. [default: all].
For a given axisymmetric
disk with all particles on circular orbits squashing the orbits a bit would
give a reasonable approximation for elliptical orbits, say by 10%:
set e=1.1
snapscale in=mod.axi out=mod.ell "rscale=sqrt($e),1/sqrt($e),1" \
"vscale=$e,1/$e,1"
snapvirial(1NEMO)
, snapshift(1NEMO)
, snapshot(5NEMO)
Joshua
E. Barnes, Peter Teuben
~/src/pjt/nbody snapscale.c snapscale.1
7-May-87 V1.0: created PJT
16-Nov-87 V1.1: mass added PJT
9-Mar-88 V1.2: data history added, proper debug output PJT
16-Mar-88 V1.0 at IAS by Josh JEB
1-Jun-88 V2.0: merged PJT extensions into JEB’s code PJT
24-aug-88 V2.1: added pscale keyword PJT
15-aug-89 V2.4: added pscale,ascale,xscale,kscale PJT
19-oct-99 doc improved PJT
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