Figure8 Orbit

This is a phase space plot of the figure8 orbit. For a shell script that produced this figure, see below

The shell script

Here is a simple shell script using NEMO programs to produce the plot above. 
#! /bin/csh -f 
#

#  PGPLOT's default is 512 x 512
setenv PGPLOT_GIF_WIDTH 1024
setenv PGPLOT_GIF_HEIGHT 1024

#  here is an example of nbody00, which understands native snapshot file

nbody00 $NEMODAT/figure8.dat - tcrit=20 deltat=0.01 eps=0.0 debug=-1 |\
    snapprint - x,y,vx,vy |\
    tabplot - 1,1,1,2,2,3 2,3,4,3,4,4 -1.6 1.6 -1.6 1.6 \
            color=2,3,4,5,6,7 \
            xlab="x=Red x=Green x=Blue y=LightBlue y=Purple y=Yellow" \
            ylab="y=Red vx=Green vy=Blue vx=LightBlue vy=Purple vy=Yellow" \
	    headline="Figure8 phase space (nbody00)" \
	    yapp=figure8.gif/gif


# here is an example of an integrator that understands ascii files

snapprint $NEMODAT/figure8.dat m,x,y,z,vx,vy,vz header=t newline=t |\
    nbody_sh1 -i -o 0.01 -t 20 |\
    tabtos - - nbody,time m,x,y,z,vx,vy,vz nbody=3 debug=-1 |\
    snapprint - x,y,vx,vy |\
    tabplot - 1,1,1,2,2,3 2,3,4,3,4,4 -1.6 1.6 -1.6 1.6 \
            color=2,3,4,5,6,7 \
            xlab="x=Red x=Green x=Blue y=LightBlue y=Purple y=Yellow" \
            ylab="y=Red vx=Green vy=Blue vx=LightBlue vy=Purple vy=Yellow" \
            headline="Figure8 phase space (nbody_sh)" \
            yapp=figure8.gif/gif
The output - at least in Feb 2004 - of these two scripts was as follows:

the nbody00 example 

x y vx vy
### Warning [nbody00]: You have hit upon an F2DOT=0 case, correcting....
read 6003 points
min and max value in xcolumns 1,1,1,2,2,3: [-1.107690 : 1.107670]
min and max value in ycolumns 2,3,4,3,4,4: [-1.107690 : 1.107670]

the nbody_sh1 example 

m x y z vx vy vz
x y vx vy
Starting a Hermite integration for a 3-body system,
  from time t = 0 with time step control parameter dt_param = 0.03  until time 20 ,
  with diagnostics output interval dt_dia = 1,
  and snapshot output interval dt_out = 0.01.
at time t = 0 , after 0 steps :
  E_kin = 1.21286 , E_pot = -2.5 , E_tot = -1.28714
                absolute energy error: E_tot - E_init = 0
                relative energy error: (E_tot - E_init) / E_init = -0
at time t = 1.00963 , after 90 steps :
  E_kin = 1.2152 , E_pot = -2.50234 , E_tot = -1.28714
                absolute energy error: E_tot - E_init = -3.33568e-10
                relative energy error: (E_tot - E_init) / E_init = 2.59154e-10
...
at time t = 19.0027 , after 1675 steps :
  E_kin = 1.21359 , E_pot = -2.50074 , E_tot = -1.28714
                absolute energy error: E_tot - E_init = -1.10575e-07
                relative energy error: (E_tot - E_init) / E_init = 8.59076e-08
at time t = 20.0111 , after 1765 steps :
  E_kin = 1.21337 , E_pot = -2.50052 , E_tot = -1.28714
                absolute energy error: E_tot - E_init = -1.19831e-07
                relative energy error: (E_tot - E_init) / E_init = 9.30987e-08
read 6003 points
min and max value in xcolumns 1,1,1,2,2,3: [-1.107670 : 1.107670]
min and max value in ycolumns 2,3,4,3,4,4: [-1.107670 : 1.107670]