Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1997
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1997

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Re: Getting values from a Plot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg7495] Re: [mg7483] Re: Getting values from a Plot
  • From: Allan Hayes <hay at haystack.demon.co.k>
  • Date: Sat, 7 Jun 1997 03:48:14 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

There can be problems with using	
	Plot[....][[1,1,1,1]]
to get the list of coordinates when the plot is in two parts (eg.  
Sqrt[x^2-1]), which we may not detect in advance, or when PlotStyle  
has been used.
The alternative
	Cases[Plot[....], Line[x]->x, Infinity]
deals with these.
Of course it will pick up all lines, for example, any from Epilog  
and Prolog - these could be excluded by
	Cases[Plot[....][[1]], Line[x]->x, Infinity]

(1) the plot may be in two parts.

pl = Plot[Sqrt[x^2-1],{x,-2,2}]

pl[[1,1]]
	{Line[{{-2.,1.73205},...,{-1.00082,
        	0.0404806}}],
 	 Line[{{1.00166,0.057683},...,{2.,1.73205}}]
	 }

We get the coordinates of only the first one

pl[[1,1,1,1]]

	{{-2.,1.},{-1.83773,0.915277},... ,{-1.00082,0.0286183}}


(2) We may have used PlotStyle

pl2 =Plot[Sin[x],{x,-1,1},PlotStyle->Hue[0]]

pl2[[1]]
	{Hue[0],{Line[{{-1.,-0.841471},...,{1.,0.841471}}]}}


Allan Hayes
hay at haystack.demon.co.uk
http://www.haystack.demon.co.uk/training/html
voice:+44 (0)116 2714198
fax: +44 (0)116 2718642
12 Copse Close, Leicester, LE2 4FB, UK


  • Prev by Date: Unfinished machine arithmatic
  • Next by Date: Re: Re: Abs and Sign anomolies
  • Previous by thread: Re: Getting values from a Plot
  • Next by thread: How can I get Mathlink Developer's Kit for v3.0 student ?