       Re: Is it possible to query current plot range values (or have

• To: mathgroup at smc.vnet.net
• Subject: [mg110764] Re: Is it possible to query current plot range values (or have
• From: "David Park" <djmpark at comcast.net>
• Date: Mon, 5 Jul 2010 06:02:48 -0400 (EDT)

```The Presentations package has a command, DrawingWidths2D, that gives
knowledge of the bounding box of a set of graphics primitives, which can be
used while drawing other primitives. It returns the x and y ranges, the x
and y centers, and the min and max values of the bounding box.

For example, here we use it to find the bounding box of an ellipse produced
by a ContourPlot.

Needs["Presentations`Master`"]

quadratic[x_, y_] := x^2 + 2 x y + 1.5 y^2 + 3 x - y + 2
{{xrange, yrrange}, {xccenter,
ycenter}, {{xmin, xmax}, {ymin, ymax}}} =
DrawingWidths2D[{ContourDraw[
quadratic[x, y] == 0, {x, -15, 15}, {y, -15, 15}]}]

{{9.94158, 8.11799}, {-5.50227,
4.00035}, {{-10.4731, -0.531481}, {-0.0586483, 8.05934}}}

Here we use it to draw the ellipse and then add a vertical line that matches
the vertical range.

Module[{g, xrange, yrange, xcenter, ycenter, xmin, xmax, ymin, ymax},
g = ContourDraw[quadratic, {x, -15, 15}, {y, -15, 15},
PlotRange -> All];
{{xrange, yrrange}, {xcenter,
ycenter}, {{xmin, xmax}, {ymin, ymax}}} = DrawingWidths2D[{g}];
Draw2D[
{g,
Line[{{xcenter, ymin}, {xcenter, ymax}}]},
PlotRange -> All,
ImageSize -> 300]
]

David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/

From: Leo Alekseyev [mailto:dnquark at gmail.com]

Some of my plots contain vertical lines for alignment.  To make sure
the lines extend from the top to the bottom of the plot frame, I
typically give those lines large values for +y and -y coordinates.
This has an unfortunate side effect that the directive PlotRange->All
now considers my line to be a part of the plot, and rescales the plot
range to display it in its entirety.  Is there a way to (a) either
make PlotRange->All ignore this line somehow or (b) set the +y and -y
coordinates of the line to match the current plot range?..

Thanks in advance to anyone who might clarify this...
--Leo

```

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