Re: Vertical Lines (Boundaries)

• To: mathgroup at smc.vnet.net
• Subject: [mg4818] Re: Vertical Lines (Boundaries)
• From: Harald Berndt <hberndt9 at mail.idt.net>
• Date: Fri, 20 Sep 1996 01:12:40 -0400
• Organization: IDT Corporation
• Sender: owner-wri-mathgroup at wolfram.com

```Larry Smith wrote:
>
> After talking to Tech Support today I was able to get a short term fix for
> a problem that I have encountered.
>
> Example:  Plot the equation y=x^2 and show boundaries at x=1 and x=2
> (vertical lines).  Is there an easy way to do this?
>
> The problem could also be asked where you need to use implicit plotting
> ImplicitPlot[x=y^3,{x,0,3}] and have y horizontal lines at y=1 and y = 2.
> Any suggestions?
>
> So far I only have the following:
>
> Show[Graphics[Line[{{1/2,-1,{1/2,8}}]], DisplayFunction -> Identity]
>
> Plot[x^2,{x,0,2},DisplayFunction -> Identity]
>
> Then combine the previous Out[] which in this case was Out[10] Graphics,
> and Out[11] Graphics
>
> Show[%10,%11, DisplayFunction -> \$DisplayFunction]
>

Needing many customizations of plot output, I have really come to
appreciate the Epilog and Prolog options available in all (I think)
plotting functions. In your example, you could simply render the lines
you need by

ImplicitPlot[yourEquation,yourDomain, Epilog ->
{Line[{startPt, endPt}]
]

or

ImplicitPlot[yourEquation,yourDomain, Prolog -> {
anyAndAllOfYourGraphicsPrimitives
}
]

Prolog is the better choice if you specify style options to
distinguish border lines and graph and want the graph to be _in front_
of the border lines (Prolog directives are rendered before the rest of
the plot). Example:

ImplicitPlot[x == y^3,{x,0,3},
PlotStyle -> {GrayLevel[0],
Thickness[0.003]
},
Prolog -> {
GrayLevel[0.5], Thickness[0.01],
Line[{{.5, -1}, {.5, 8}}],
Line[{{2, -1}, {2, 8}}]
}
]

(Note that you'll have to specify PlotStyle in the plot, otherwise the
graph will be rendered with the styles set in the Prolog.)
--
______________________________________________________________________
Harald Berndt, Ph.D.                              Research Specialist,
Consultant

Phone:	510-652-5974                                FAX:			510-215-4299
______________________________________________________________________
"I yam what I yam"...................................Popeye the sailor
(Kryten:............"I thought that was Descartes!"..................)
(Lister:............"So did I. mon, so did I!".......................)

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```

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