&FIELD: PLOT-FIELD
Produces a plot of the lines of equal function values. The contours
are labeled with the function value if the LABEL option is on (which
is by default the case).
The function is computed on the part of the viewing plane that is
located within the current AREA box.
If you request AUTOMATIC scaling of the range, contours are drawn
at round values of the function over a range that covers the function
values in the current AREA. The number of contours is used to compute
a first estimate of the distance between two contours. This distance
is rounded downwards to the first 10-fold multiple of 1, 2 or 5. The
number of contours actually drawn is therefore usually larger than
the number you requested.
[The default function is V and the contours range by default from the
highest to the lowest potential present in the cell. By default, 20
contours are plotted.]
The function is evaluated on the track or on the curve specified
with the ON keyword.
The geometric aspects of the track, if used, should be set by means
of the TRACK command before calling PLOT. Other aspects of the track,
such as the clustering model, are not used in the present context.
A curve should be parametrised in terms of T which will run from 0
to 1. All 3 coordinates of the curve should be specified. Note that
ON expects only one argument, the parametrisation should therefore
be enclosed in quotes, e.g. 'cos(pi*t),sin(pi*t),0' would be
appropriate to describe a semi-circle in the z=0 plane.
The SCALE option can be used to force a vertical scale in the
plot, this can for instance be useful if you intend to overlay
various graphs.
If you select the PRINT option, then the values plotted in the
graph will also be printed out. Output re-routing (> file) can
be used to write the values to a file.
The number of sampling points can be set with N, default is 200.
[The default function is V.]
The function is sampled at GRID by GRID points on the part of
the current viewing plane that is located inside the AREA box.
The function values are entered in an histogram.
This kind of plot can be useful to estimate the field homogeneity,
provided the range has been tuned properly.
The automatic search for proper binning (AUTOMATIC) uses the
first few entries to set the range. Since the grid is scanned
in a regular sequence, these entries are not necessarily
representative for the entire sample, in particular if the
number of bins is small compared to the grid size. See CALL ->
BOOK_HISTOGRAM -> options -> AUTOMATIC for details on the
automatic binning procedure.
[The default function is E. The number of bins is preset to 100 and
the range is by default chosen automatically.]
The function is sampled at GRID by GRID points on the part of
the current viewing plane that is located inside the AREA box.
The function values are presented as a three dimensional plot.
The plot is first rotated by phi degrees around the z-axis and
then tilted by theta degrees from the z-axis.
This plot is decorative but it is generally agreed upon that it is
hard to extract any meaningful information from it ...
[The default function is V. The default viewing angles are 30 and 60
degrees.]
This plot shows the flow of a 3-vector sampled at GRID by GRID
points on the part of the current viewing plane that is located
inside the AREA box. The vectors are displayed like geometrical
objects.
The z-component is set to 0, if not explicitely specified. For
other than (x,y) views, this may give incorrect impressions.
If used for (Ex,Ey,Ez), which is the default, one can pick out the
location of the zeroes of the field and hence figure out roughly
what the acceptance of a wire is.
It is advisable to have roughly equal ranges in view of the scaling
that is performed on the vectors.
[The default functions are EX, EY, EZ.]
All functions (f1, f2 ... f7) should be expressions in terms of the
following quantities:
----------------------------------------------------------------------
Name Meaning
----------------------------------------------------------------------
X or R x- or r-Coordinate of a point
Y or PHI y- or phi-Coordinate of a point
Z z-Coordinate of a point
EX or ER x- or r-Component of the electric field at (x/r,y/phi,z)
EY or EPHI x- or phi-Component of the electric field at (x/r,y/phi,z)
EZ z-Component of the electric field at (x/r,y/phi,z)
E Norm of the electric field at (x/r,y/phi,z)
BX x-Component of the magnetic field at (x/r,y/phi,z)
BY y-Component of the magnetic field at (x/r,y/phi,z)
BZ z-Component of the magnetic field at (x/r,y/phi,z)
B Norm of the magnetic field at (x/r,y/phi,z)
V Electrostatic potential at (x/r,y/phi,z)
----------------------------------------------------------------------
Note: The variables BX and BY should not be used with cells that have
been described in polar coordinates.
Keyword index.
Formatted on 10/11/98.