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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*.

**in=***snap-file*- Input data is read from
*snap-file*, which must be in snapshot format. **times=***time-range*- 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". **xvar=***x-expression*- 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 is**x**. **xlabel=***x-axis-label*- Label for the X axis. The default is the expression
given for
**xvar**. **xrange=***x-axis-range*- 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**. **yvar=***y-expression*- See above. The default is
**y**. **ylabel=***y-axis-label***yrange=***y-axis-range***visib=***expression*- 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**. **psize=***expression*- Determines
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**. **color=***expression*- 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**. **crange=***color-range*- 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**. **trak=****t|f**-

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

% snapplot r100.dat xvar=etot xrange=-4:0 \ xlabel="Binding energy" yvar=jtot yrange=0:0.8 \ ylabel="Angular momentum" visib="i < 1000"

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