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I would like to compute the mean of s[t] which is given by the first equation in these coupled stochastic ordinary differential equation

p[y_, a_] := a/((1 + a)*(1 + 0.5*y)) 
q[m_] := q0/2*(1 + Tanh[(m - 0.05)/0.005]) 
q0 = 0.5;
 beta = 0.15;
 alpha = 0.15; 
gamma = .1; 
s0 = 0.038; 
sigma = 0.1; 
FF[t_] = alp (1 + Tanh[llSin[2*Pit/P0]]) /. {ll -> 10, P0 -> 1, alp -> 2}
F = ItoProcess[{
   \[DifferentialD]s[t] == ((2*p[y[t], a[t]] - 1)*s[t]  + 
        q[m[t]]*y[t]) \[DifferentialD]t + s[t]  \[DifferentialD]w1[t],
   \[DifferentialD]y[t] == (2*(1 - p[y[t], a[t]])*
         s[t]  - (0.2 (1 + FF[t]) + q[m[t]]) y[
          t]) \[DifferentialD]t + y[t] \[DifferentialD]w2[t],
   \[DifferentialD] a[t] == (a[t]*(beta*s[t]*a[t]/(1 + a[t]) -alpha)) \[DifferentialD]t + \[DifferentialD]w[t],
   \[DifferentialD]m[t] == (gamma*Exp[-s[t]/s0] - alpha*m[t]) \[DifferentialD]t},
  s[t], {{s, y, a, m}, {0.1, 0.1, 0.5, 0.1}}, t, 
  {w1 \[Distributed] WienerProcess[], 
   w2 \[Distributed] WienerProcess[], 
   w \[Distributed] WienerProcess[]}]

OO = RandomFunction[F , {0, 1, 0.01}, 8]
    ListLinePlot[OO , PlotRange -> All]

enter image description here

I want to compute the mean of these 8 curves could anybody help ? I tried Mean[OO[t]] but it does not give the answer

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  • 1
    $\begingroup$ Please include the values of all the parameters so we can run your code. $\endgroup$
    – MarcoB
    Dec 9, 2020 at 15:38
  • $\begingroup$ Something like {Mean@OO["ValueList"]} // ListLinePlot $\endgroup$
    – chris
    Dec 9, 2020 at 15:41
  • $\begingroup$ or {OO["PathTimes"], Mean@OO["ValueList"]} //Transpose//ListLinePlot $\endgroup$
    – chris
    Dec 9, 2020 at 15:55
  • 1
    $\begingroup$ these are the parameters and functions:p[y_, a_] := a/((1 + a)*(1 + 0.5*y)) q[m_] := q0/2*(1 + Tanh[(m - 0.05)/0.005]) q0 = 0.5; beta = 0.15; alpha = 0.15; gamma = .1; s0 = 0.038; sigma = 0.1; FF[t_] = alp (1 + Tanh[llSin[2*Pit/P0]]) /. {ll -> 10, P0 -> 1, alp -> 2} $\endgroup$ Dec 9, 2020 at 16:36
  • $\begingroup$ @elKettaniPerla Please edit your question accordingly with parameters in your comment. $\endgroup$ Dec 9, 2020 at 17:28

1 Answer 1

2
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proc = ItoProcess[{\[DifferentialD]x[t] == 
    v[t] \[DifferentialD]t, \[DifferentialD]v[
      t] == -x[t] \[DifferentialD]t + \[DifferentialD]n[t]}, 
  x[t], {{x, v}, {1, 0}}, t, n \[Distributed] WienerProcess[]]


path = RandomFunction[proc, {0., 2. Pi, 0.05}, 12, 
   Method -> "StochasticRungeKutta"];

pl1=ListLinePlot[path];

pl2 = {path["PathTimes"], Mean@path["ValueList"]} // Transpose // 
  ListLinePlot[#, PlotStyle -> AbsoluteThickness[4]] &;

Then

 Show[pl1,pl2]

enter image description here

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