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How do I make a phase portrait which looks like the ones demonnstrated here? Not the fancy version where I can use the controls to change it, just a screen-shotted version of say a spiral point? Any help would be massively appreciated!

http://demonstrations.wolfram.com/PhasePortraitAndFieldDirectionsOfTwoDimensionalLinearSystems/

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  • $\begingroup$ Why don't you download the demonstration and study the code it contains? $\endgroup$
    – m_goldberg
    Mar 12, 2015 at 11:43
  • $\begingroup$ Use StreamPlot function. $\endgroup$
    – Vladimir
    Mar 12, 2015 at 11:46
  • $\begingroup$ Basins of Attraction $\endgroup$
    – Artes
    Mar 12, 2015 at 12:27
  • $\begingroup$ Welcome to Mathematica.SE! I suggest that: 1) You take the introductory Tour now! 2) When you see good questions and answers, vote them up by clicking the gray triangles, because the credibility of the system is based on the reputation gained by users sharing their knowledge. Also, please remember to accept the answer, if any, that solves your problem, by clicking the checkmark sign! 3) As you receive help, try to give it too, by answering questions in your area of expertise. $\endgroup$
    – bbgodfrey
    Mar 23, 2015 at 4:05

1 Answer 1

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Taking the code practically straight out of the author's demo:-

m = {{1, -3.5}, {2, -2}};

pt1 = {-5.1, 4.8};
pt2 = {4.9, 5.1};
pt3 = {-4.9, -5};
pt4 = {4.9, -5.2};

Show[VectorPlot[m.{x, y}, {x, -10, 10}, {y, -10, 10},
  StreamPoints -> {{pt1, pt2, pt3, pt4}},
  StreamStyle -> {Red, Thick}, ImageSize -> {460, 310}],
 Graphics[
  {Thick, Orange, Map[Line[{-100 #, 100 #}] &,
    Select[Eigenvectors[m], (Im[#[[1]]] == 0 && Im[#[[2]]] == 0) &]]}],
 PlotLabel -> Row[{Column[{Row[{Column[
         {Style["\!\(\*OverscriptBox[\(x\), \(.\)]\)", Italic], 
          Style["\!\(\*OverscriptBox[\(y\), \(.\)]\)", Italic]}],
        Column[{" = ", " = "}],
        TableForm[m.{Style["x", Italic], Style["y", Italic]}] // N}]}], "  ", 
    Column[{"Eigenvalues:", 
      NumberForm[Chop@N@Eigenvalues[m], {4, 2}]}], "  ", , 
    Column[{"Eigenvectors:", 
      NumberForm[Chop@N@Eigenvectors[m][[1]], {4, 2}], 
      NumberForm[Chop@N@Eigenvectors[m][[2]], {4, 2}] }]}]]

enter image description here

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