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