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Topic: Vertical Lines (Boundaries)
Replies: 1   Last Post: Sep 20, 1996 12:48 AM

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Harald Berndt

Posts: 6
Registered: 12/7/04
Re: Vertical Lines (Boundaries)
Posted: Sep 20, 1996 12:48 AM
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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}]


ImplicitPlot[yourEquation,yourDomain, Prolog -> {

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],
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,

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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