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snapstat - compute various statistics of an N-body snapshot
snapstat
in=snapshot_file [parameters=values...]
snapstat provides various
statistics of an N-body snapshot, such as moments in phase space, various
radii (such as mass-fraction radii, virial radius and core radius) and generalized
surface density, total energetics. For particles with binding energy larger
than a specifief amount a shape analysis is done.
The following
parameters are recognized in any order if the keyword is also given:
- in=in_file
- Input data are read from in_file, which must be in standard SnapShot(5)
format [No default].
- times=range
- Range of times to do the analysis on. E.g.
"0:10,12,13" [default: all].
- exact=t|f
-
- minradfrac=value\fP
- Fudge factor,
smaller than but not too close to 1, for core-radius determination. A better
algorithm is expected in some future version [default: 0.1].
- all=t|f
- This
overrides all other subsequent logicals (exept exact) who determine what
parameters to determine for the system [default: false].
- pot=t|f
- Logical
if to determine energetics (potential en kinetic) of system. This is a
time consuming (N*N) part [default: false].
- eps=value
- Value of the softening
length for potential energy calculation [default: 0.025].
- r_h=t|f
- Logical
if to determine the fractional mass radii of the system. Currently implemented
it will return radii at which the mass fraction is 10%..90% in steps of 10%
[default: false].
- r_v=t|f
- Logical if to determine the virial radius of the
system. This is a time consuming (N*N) part [default: false].
- r_c=t|f
- Logical
if to determine the core radius of the system [default: false].
- rms=t|f
- Logical
if to determine the full rms velocity dispersion of the system [default:
false].
- ecutoff=value
- Value of the energy above which the particles will
be discarded from a shape analysis. [default: 0.0, i.e. only verbose=t|f Logical
if you need a lot of explanatory text around your numbers. The false option
is often used to make tables for further plotting using plotting packages
as Mongo(1)
[default: false]
snapkinem(1NEMO)
,snapshot(5NEMO)
The
algorithm to determine the core radius is noisy.
Shape analysis is a straight
moment analysis, and hence perhaps too heavily weighted for particles at
large radii.
Keyword verbose is not fully implemented yet in V1.3.
Peter
Teuben
~/src/pjt/nbody snapstat.c snapstat.1
9-Jan-87 V1.0: created PJT
24-Jul-87 V1.1: cleanup up, doc written PJT
10-Nov-87 V1.3: output enhancements, improved doc PJT
7-jun-88 V1.4: new filestruct PJT
24-aug-88 V1.4a: cleanup PJT