Table of Contents

Name

snapstat - compute various statistics of an N-body snapshot

Synopsis

snapstat in=snapshot_file [parameters=values...]

Description

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.

Parameters

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]

See Also

snapkinem(1NEMO) ,snapshot(5NEMO)

Bugs

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.

Author

Peter Teuben

Files


~/src/pjt/nbody     snapstat.c snapstat.1

Update History


 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