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Use the "Plot Type" toggle to select the type of plot you would like
to display.  If only one plot is displayed, that plot
will be immediately re-displayed as the new plot type. If more than one
plot is displayed, a list widget will come up so that one may select which
plot(s) should be changed to the new plot type.   If some plots are hidden,
those plots will not appear in the list widget, as one may only change the
plot type of a displayed plot, not one that is hidden.  
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The following is a list of different plot types:
.sp
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.IP "3D     "
3D plots are comprised of a line connecting each value along the X axis.
The plot is formed of a series of connected lines stacked in the Y
direction.
.IP "Scatter "
Scatter plots interpret input as a set of individual points, and
are displayed as such.
.IP "Impulse"
Impulse plots are formed by extending a line from the floor of the 3D plot,
which is usually the X-Y plane, upward in the Z direction.  The height of
each line in the plot represents the value at that particular location.
.IP "Mesh   "
Mesh plots are much like 3D plots, but are pictured as a surface made up
of polygons rather than as a set of lines.
.IP "Horizon"
A Horizon plot is a surface plot that is drawn from the rear to the front.
This implies that the under surface will be filled.
.IP "Surface"
Surface plots are similar to Mesh plots, except the surface is colored in,
rather than being represented as a series of connected lines.
.IP "Contour 3D"
3D Contour plots are similar to 2D Contour plots in that the contour lines
supply depth information; however, the 3D information is not
cast onto the XY plane, but is left in three dimensions. Again, the different
contour levels are represented by their colors, but depth information is
also represented by their position in the 3D space. Thus, 3D contour plots
are more useful for printouts and monochrome workstations, as depth is provided
by positioning as well as color.
.IP "Contour 2D"
2D Contour plots are a special case, as they take three dimensional
information but are displayed in a two dimensional space. Contour plots
cast the information onto the XY plane; the contour lines on the XY plane
supply depth information, as in aerial photography and relief
maps.  On a color display, the different contour levels are represented in 
different colors, in ROYGBIV order (red, orange, yellow, green,
blue, indigo, violet), where violet represents the smallest depth value
(Z value) and red represents the largest depth value (Z value).
Unfortunately, contour maps loose much in the translation to a
monochrome machine, as there is no way represent depth.
.IP "Color Mesh"
Color Mesh plots are similar in structure to Mesh plots, except that the
lines making up the mesh are colored.  The color is a function of the
height of the values in the Z direction.
