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Re: Graphing sets of linear inequalities


Here are two methods for making your plot.

<< Graphics`FilledPlot`
<< Graphics`Colors`
<< Graphics`InequalityGraphics`

The first method used FilledPlot. We need to change your inequalities into
one for y values.

-2 < x + 2y < 4;
(# - x)/2 & /@ %
(1/2)*(-2 - x) < y < (4 - x)/2

FilledPlot[{(1/2)*(-2 - x), (4 - x)/2}, {x, -2, 4},
   Fills -> LightCoral,
   AspectRatio -> Automatic,
   Frame -> True,
   FrameLabel -> {x, y},
   Axes -> None,
   PlotLabel -> -2 < x + 2*y < 4,
   Background -> Linen,
   ImageSize -> {450, Automatic}];

The second method is to use InequalityPlot.

InequalityPlot[
    -2 < x + 2y < 4, {x, -2, 4}, {y, -3, 3},
    Fills -> LightCoral,
    Frame -> True,
    FrameLabel -> {x, y},
    Axes -> None,
    PlotLabel -> -2 < x + 2y < 4,
    Background -> Linen,
    ImageSize -> {450, Automatic}];

Note that a liberal use of plot options are often necessary to make a nice
looking plot.

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/




From: DJ Craig [mailto:spit at djtricities.com]
To: mathgroup at smc.vnet.net

How do you graph something like this:
-2 = x + 2y = 4
I need the areas where this is true to be shaded, and solid lines at x
+ 2y = -2 and x + 2y = 4.




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