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Re: Drowing a vertical or horizontal line in a graphic

• To: mathgroup at smc.vnet.net
• Subject: [mg77282] Re: Drowing a vertical or horizontal line in a graphic
• From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
• Date: Wed, 6 Jun 2007 07:12:52 -0400 (EDT)
• Organization: The Open University, Milton Keynes, UK
• References: <f43h19$2sm$1@smc.vnet.net>

Vicent wrote:
> I am using Mathematica 5 and I have a simple question to ask you.
> 
> I am drawing a function with "Plot" function.
> 
> How can I add a vertical or horizontal line (or several ones) at a
> given position?
> 
> For example, I want to draw   y = (x-1)^2, and also want a vertical
> line just at  x = 1,  in order to signal the point where that fuction
> gets its lower value.
> 
> How can I do it?
> 
> Thank you in advance.
> 
> --
> Vicent

Hi Vicent,

I suggest using the graphic primitive Line in the Epilog part of the 
Plot command so you can easily control attributes such as color or 
thickness for each of the lines or points you wish to emphasize. For 
instance,

In[1]:=
Plot[(x - 1)^2, {x, -1, 3},
   Epilog -> {Red, Thickness[0.02], Line[{{1, 0}, {1, 4}}]}]

Regards,
Jean-Marc