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snapmradii - print lagrangian mass radii in a snapshot


snapmradii in=in_file [parameter=value] ...


snapmradii prints a table of the fractional lagrangian mass-radii of a snapshot. The snapshot will be sorted internally by increasing radius (which can be changed by using sort=), there is no need to use snapsort(1NEMO) preceding this call.

See radprof(1NEMO) to get the cumulative mass radii for each particle.


The following parameters are recognized:
input file, in snapshot format. Default: none.
Fractional mass radii. They must be sorted and between 0 and 1 (inclusive). [Default: 0.1:0.9:0.1]
Output in the form of a table of mass fraction vs. radius? The normal output mode is one snapshot per output row, with time, and the mass fractions [Default: f]
Output the radii in logarithmic units [Default: f]
Sorting variable used to sort the particles. Any bodytrans(3NEMO) expression can be used. Default: r. Default


The following example shows the evolution of 10%-90% lagrangian mass radii and outputs the result in a graph and a pretty printed table
  hackcode1 out=snap.dat tstop=10 freqout=5
  snapmradii snap.dat | tabplot - line=1,1
  snapmradii snap.dat | column -t
  0        0.441198  0.571462  0.677862  0.765226  0.822322  0.858481  0.889645
 0.918198  0.960976
  0.21875  0.396341  0.570931  0.652903  0.745234  0.791166  0.844938  0.893917
 0.958933  1.00103
  0.40625  0.399102  0.479913  0.628671  0.707029  0.785033  0.829081  0.907681
 0.986865  1.06195

The following example shows the cumulative mass distribution function for the third snapshot in a large simulation, and plots it:

    snaptrim snap.dat - times=#3 | snapmradii - 0.01:0.99:01 |\
            tabplot - xlab="Mass fraction" ylab=Radius


Doesn’t handle snapshots with zero mass very well.

Doesn’t deal with snapshots where there is no stars in one of the fraction bins requested. Since linear interpolation is used, some crazy larger radius is reported.

See Also

snapcenter(1NEMO) , snapstat(1NEMO) , snapprint(1NEMO) , radprof(1NEMO) , column(1)

W.L.Sweatman - (1993) MNRAS 261, 497.


Peter Teuben


~/src/nbody/reduc       snapmradii.c 

Update History

12-May-92    V1.0: created              PJT
10-aug-95    V1.2: added tab=     PJT
15-aug-96    V1.3: fixed bug which assumed total mass =1 PJT
27-jul-05    V1.5: add sort=        PJT
1-apr-21    V1.6: handle massless snapshots for Tjeerd    PJT

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