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What is wrong with my code below

f1[ar_, cj_, mj_, tj_, kj_, s_, w_] := 
ar*J[t] + cj*R[t] + mj*J[t] - tj*R[t] - kj*J[t] + s*R[t]*J[t] + w*J[t]*R[t];
g1[aj_, cr_, mr_, tr_, kr_, s_, w_] := 
aj*R[t] + cr*J[t] + mr*R[t] - tr*J[t] - kr*R[t] - s*R[t]*J[t] - w*J[t]*R[t];

splot = StreamPlot[{f[1, 1, 0, 0, 1, 1], g[1, 1, 0, 0, 1, 1]}, {J, -4,4},{R, -4, 4}];
Manipulate[Show[splot,ParametricPlot[Evaluate[First[{x[t], y[t]} /.
NDSolve[{J'[t] == f1[1, 1, 0, 0, 1, 1], R'[t] == g1[1, 1, 0, 0, 1, 1], 
Thread[{x[0], y[0]} == point]}, {x, y}, {t, 0, T}]]], {t, 0,T}, PlotStyle -> Red]],
{{T, 10}, 1, 100}, {{point, {1, 0}}, Locator}, SaveDefinitions -> True]

I am getting the error ConstantArray::ilsmn: Single or list of non-negative machine-sized integers expected at position 2 of ConstantArray[{J,R},-\[Infinity]].

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  • 1
    $\begingroup$ This is not a free debugging service... $\endgroup$
    – Henrik Schumacher
    Dec 5, 2018 at 22:27
  • $\begingroup$ I don't really understand the error in my code, that is why I am asking it here. I thought this was one of the purpose of the site. If you can help, or point me to the right direction, it will be much appreciated. $\endgroup$
    – DMH16
    Dec 5, 2018 at 22:29
  • $\begingroup$ It would have be easy for you to find out that Manipulate and ParametricPlot. The error occurs already when executing NDSolve[{J'[t] == f1[1, 1, 0, 0, 1, 1], R'[t] == g1[1, 1, 0, 0, 1, 1], Thread[{x[0], y[0]} == point]}, {x, y}, {t, 0, T}]. You try to solve for x and y but the equations are in terms of J and R. And you defined f1 and g1 as functions in seven variables but you call them only with six variables. NDSolve[{ J'[t] == f1[1, 1, 0, 0, 1, 1, 1], R'[t] == g1[1, 1, 0, 0, 1, 1, 1], Thread[{J[0], R[0]} == point] }, {J, R}, {t, 0, T}] seems to work. $\endgroup$
    – Henrik Schumacher
    Dec 5, 2018 at 22:32
  • $\begingroup$ @HenrikSchumacher Thanks for the reply but your code is still giving errors. I don't really understand the errors $\endgroup$
    – DMH16
    Dec 5, 2018 at 22:41
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    $\begingroup$ @DMH16 I think the title of your post should at least attempt to describe the problem you are facing. Presently 95 % of the posts in this SE could be called what is wrong with my code... $\endgroup$
    – chris
    Dec 6, 2018 at 1:19

1 Answer 1

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after fixing a lot of typos, the code works

f1[ar_, cj_, mj_, tj_, kj_, s_, w_, R_, J_] := 
  ar*J + cj*R + mj*J - tj*R - kj*J + s*R*J + w*J*R;
g1[aj_, cr_, mr_, tr_, kr_, s_, w_, R_, J_] := 
  aj*R + cr*J + mr*R - tr*J - kr*R - s*R*J - w*J*R;

splot = StreamPlot[{f1[1, 1, 0, 0, 1, 1, 1, R, J], 
   g1[1, 1, 0, 0, 1, 1, 1, R, J]}, {J, -4, 4}, {R, -4, 4}]
Manipulate[
 Show[splot, 
  ParametricPlot[
   Evaluate[
    First[{R[t], J[t]} /. 
      NDSolve[{J'[t] == f1[1, 1, 0, 0, 1, 1, 1, R[t], J[t]], 
        R'[t] == g1[1, 1, 0, 0, 1, 1, 1, R[t], J[t]], 
        Thread[{R[0], J[0]} == point]}, {R, J}, {t, 0, T}]]], {t, 0, 
    T}, PlotStyle -> Red]], {{T, 10}, 1, 100}, {{point, {1, 0}}, 
  Locator}, SaveDefinitions -> True]

fig1

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