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snapplot, trakplot - display an N-body snapshot file
insnap-file [parametervalue] ...
snapplot plots a sequence of frames
from a standard N-body snapshot file on a yapp(5NEMO)
display device. trakplot
is an old name of snapplot that would not erase and redraw the screen
after each frame plotted, and could thus be used to show the orbit of
the selected points. The later added (boolean) keyword trak= (see below)
should now be used to explicitly set the ’trak’ing mode. See also the stack=
option in snapgrid(1NEMO)
Arbitrary (algebraic) transformations from particle
coordinates to plotting coordinates may be specified; the visibility, point
type, and color may be controled in the same way.
In the yt package this
is known as PhasePlot.
The following parameters are recognized;
they may be given in any order.
handles arbitrary C expressions by invoking the compiler, which is general
but rather slow. To speed things up, the expressions are first treated as
names and checked against a collection of precompiled expressions stored
as ".o" files. If a match is found, the precompiled object is used instead.
Precompiled transformations include: x, y, z, vx, vy, vz, r, v, vr, vt,
jtot, phi, etot, t, and i. A complete list may be deduced by looking in
.../nemo/obj/bodytrans/, which is the default repository. It is possible to
customize your own transformations and mantain alternate collections; see
for more information.
Plot snapshot file "r100.dat"
frame-by-frame, with default transformations:
- Input data is read from snap-file,
which must be in snapshot format.
- Only plot frames with
time values within time-range, which is of the form, eg, "1.0:1.5,2.5,3.0". The
default is "all".
- The value of x-expression is plotted along
the X axis. x-expression is a real-valued C language expression over the real
values x, y, z, vx, vy, vz, phi, t, and the integer value i. The default
- Label for the X axis. The default is the expression
given for xvar.
- Range of values for the X axis, specified
either as a single number (in which case the lower bound is zero) or a
pair of numbers separated by a colon. The default range is -2.0:2.0.
- See above. The default is y.
- Determines the visibility of particles. expression is a integer expression
in the above variables; only points with non-zero values are plotted. Particles
are plotted in order of their visib, e.g. visib=1 are plotted before visib=2,
thus this keyword can be used to re-arrange the plotting order on screen
(useful if colors are used). The default is 1.
the point type and size. expression is a real expression in the above variables;
zero means plot a point, positive (negative) means plot a circle (cross)
with size controled by absolute value. The default is 0.
- Determines the point color. expression is a real expression in the above
variables; values between 0 and 1 produce a sequence of saturated colors
starting with red, running through the spectrum, and wrapping back to red.
The default is 0.
- Range of colors that should be mapped.
Below and above these ranges the yapp(3NEMO)
plotting layer may determine
the visibility of the points. The default range is 0:1.
Plot radius vs radial velocity at times 2.0 through 6.0:
% snapplot r100.dat
Plot binding energy vs angular momentum, showing only the first 1000 particles:
% snapplot r100.dat xvar=r xrange=0:2 yvar=vr times=2:6
NB: this last example assumes that "r100.dat" includes potential data in
addition to the usual phase-space data. The expression specified for visib
will be passed to the C compiler.
The default ranges should depend on the variables plotted.
% snapplot r100.dat xvar=etot xrange=-4:0 \
xlabel="Binding energy" yvar=jtot yrange=0:0.8 \
ylabel="Angular momentum" visib="i < 1000"
28-apr-04 documented history PJT
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